WITH trucks and chain saws they rumble into the national forests when no one is looking, toppling giant trees and making off with thousands of dollars in valuable timber.
They move the stakes that designate where logging is allowed. They steal the special paint used to mark trees for legal cutting. They fiddle with scales used to determine the value of logs.
And sometimes they do it in collusion with the federal employees whose job is to protect the nation's forests.
They are woods rustlers, timber thieves who may be costing taxpayers as much as $100 million or more each year, according to congressional investigators.
''It's happening today as we speak, and it'll happen tomorrow,'' says James Keefer, a United States Forest Service (USFS) investigator.
The problem is not only a loss of public resources and revenue but also damage to the environment, particularly now that ''ecosystem management'' has become the guiding philosophy in taking care of federal forests.
''Without control of the theft problem, our ability to manage the national forests as responsible stewards is severely compromised,'' says Jack Ward Thomas, chief of the Forest Service.
Mr. Thomas recently named a new director of law enforcement and investigations for the USFS. ''Stealing from national forests will not be tolerated,'' he says.
Fulfilling that pledge is a massive job. Spread over 191 million acres of federal forests, the 700 Forest Service law enforcers would have to patrol an average of more than a quarter-million acres each. But many of those 700 hold desk jobs, and the special Timber Theft Investigations Branch, set up in 1991, has only about a dozen members for the whole country.
Another part of the problem, critics say, is that the agency is too close to the timber industry.
''Forest Service people and timber company people come from the same place; they're all on the same team,'' asserts Jason Eisdorfer, a former special assistant US attorney with the Department of Agriculture, which oversees the Forest Service. ''It's a whole systematic kind of mindset.''
''That partnership [between industry and government] was not always an honest one,'' says Mr. Keefer, a member of a special task force of the US Forest Service investigators. In one recent case, a district ranger was indicted for making false statements and submitting false documents regarding a timber sale. That case is now before a grand jury.
Last week, 16 environmental groups petitioned the US Justice Department to investigate charges that the Forest Service has obstructed timber theft probes. Among the groups signing the petition are the Sierra Club, the National Audubon Society, Friends of the Earth, and Greenpeace.
The petition from environmentalists was prompted by a report published by the Montana-based group Voice of the Environment. Titled ''Chainsaw Justice,'' the six-month investigation concluded that ''millions of dollars of trees -- from the rain forests in Alaska to the hardwood groves of North Carolina -- are being illegally logged, often with the help of the US government.''
''USFS managers have aided and abetted timber thieves by tampering with evidence, tipping off industry about ongoing criminal investigations, and granting industry access to 'tracer paint,' which is then used to mark trees-to-be-cut outside legal boundaries, according to several of the Service's own law enforcement agents,'' the report states.
Some timber theft involves no more than a pickup truck full of purloined firewood. But with a single log truck able to carry $4,000 to $5,000 in timber at today's prices, there have also been much larger cases. Individuals and companies have paid as much as $1.7 million in fines and restitution for single cases of theft or receipt of stolen property.
A Lear jet, a Ferrari, and several homes were seized in conjunction with $20 million in alleged timber theft in southern Oregon and northern California. Prison sentences have been meted out as well.
In citing such figures, Forest Service chief Thomas emphasizes that ''the vast majority'' of timber companies support government efforts to stop timber theft.
Some members of the special timber theft task force, which reports directly to Forest Service headquarters in Washington rather than up the chain of command through the agency's nine regional offices, allege that their work ''has drawn a powerful backlash from entrenched agency officials on whose watch timber theft reeled out of control.''
In a letter to Forest Service chief Thomas last September, 10 members of the task force (more than half the special investigators) said they had suffered ''reprisals'' and ''ugly, institutional retaliation'' as a result of their work.
These agents and several others, now are represented by attorneys with the Government Accountability Project, a public- interest group that works on behalf of government whistle-blowers.
''We're deviating from the old guard,'' says one task force member. ''Every case we make, the Forest Service looks bad. We run the dirty laundry up the pole. There's a strong need to change the system and tighten up.''
''I have been threatened,'' adds this source, who recently was anonymously charged with misusing a government vehicle.
When he was appointed 15 months ago as the first biologist to head the agency, Forest Service veteran Thomas told his 35,000 employees to ''obey the law and tell the truth.'' The strong public stand for ethics came as a relief to many in the agency troubled by what they saw as an entrenched tradition of ''getting out the cut'' to the detriment of forest health.
A University of Washington survey of Forest Service employees last year showed two-thirds believing that timber-harvesting practices could not be sustained over the next century.
In response to the letter from the timber theft task force members last fall, Thomas asked the USDA inspector general to investigate the charges, and he met personally with task force members.
''He listened to them, he laughed with them, cried with them, hugged them, told them he was committed to the same things they were fighting for, that he would stand behind maintaining a national strike force and go after the largest [timber theft] cases,'' says Thomas Devine, legal director of the Government Accountability Project. ''Since then, he's been pretty much true to his word.''
He adds: ''The harassment pretty much stopped, and for the last three months the TTIB [Timber Theft Investigations Branch] has been able to again go back to investigating pretty much full steam ahead.''
For now, the task force is zeroing in on three major timber theft cases. The cases cross Forest Service regional boundaries, and some agency employees are suspected of wrongdoing.
But whether the task force will remain independent and get the resources supporters say it needs remains to be seen. As the internal power struggle at the Forest Service unfolds, chief Thomas is said to be under pressure from within the agency to disperse the special agents to the regions.
''From one perspective, that makes sense,'' Mr. Devine says. ''The ultimate goal of most of these agents is to go back to the regions. But in the short term that would be disastrous. For one thing, there's a big conflict of interest. Some of these regions are very explicit targets of timber theft fraud investigations. It would be like assigning a defendant to carry on the prosecution on the verge of a trial.''
There also have been calls for broader Forest Service reform: being more environmentally aware, ending the below-cost timber sales that mean more than one-third of all national forests are money-losers, cutting industry subsidies for things like building log roads.
''There's room for hope, but change is happening much too slowly,'' says Doug Hiken of the Association of Forest Service Employees for Environmental Ethics, a 1,000-member group based in Oregon. ''Jack Ward Thomas has come out with a lot of excellent rhetoric, and maybe it's slowly beginning to sink in.
''But,'' he adds, ''there's still a lot of scary stuff going on.''