Speculation is increasing that sabotage was behind the midair plane explosion Wednesday that killed Pakistan's President, Mohammed Zia ul-Haq, the United States ambassador to Pakistan, Arnold Raphel, and 28 others. ``Evidence seems to indicate that it wasn't a haphazard accident,'' said a senior Pakistani official contacted by telephone. The official pointed to the ``robustness'' of the President's US-made C-130 craft; the high level of safety precautions surrounding the flight; and the lack of any distress signal.
Though Pakistani security officials are still inspecting the wreckage, located in Pakistan some 80 miles from the Indian border, the possibility that the plane collided with another aircraft or was hit by a missile has been ruled out. The US Department of Defense is sending a team to help the Pakistani investigation.
The senior Pakistani official, stressing that talk about sabotage is still only speculation, listed the three most likely groups that could have been behind the explosion: the Soviet-backed Afghan government, the Pakistani opposition group Al-Zulfikar, and India.
Of the three, the first possibility has by far the highest probability, according to the official and other analysts. As Soviet troops have withdrawn from Afghanistan, the Afghan regime has been crumbling faster than anticipated, an embarrassment to the Afghans and their Soviet patrons.
Pakistan, meanwhile, has continued to funnel US aid to the Afghan mujahideen fighters as the Soviets have continued to support the Afghans. By assassinating President Zia, the Afghans might hope to destabilize Pakistan and weaken its support for the guerrillas, the official said. After Mr. Zia's death, the Pakistani government reaffirmed its support for the resistance.
Zia had ``led resistance to the occupation,'' the Pakistani official said. ``If it weren't for almost 10 years of resistance by Pakistan and the US, the Soviets would have gotten the best of both worlds - glasnost (openness) and perestroika (reconstruction) and Afghanistan.''
In recent months, the Afghan and Soviet governments have issued a flurry of threatening statements against Pakistan, accusing it of breaking the Geneva withdrawal accords. Pakistan has also suffered a high incidence of terrorist acts, such as explosions and border raids.
``In some cases, the perpetrators were caught - they were agents of the Khad,'' the Afghan secret police, the official said.
The Soviet secret police, the KGB, trains the Khad. If it were proved that the Khad was behind Zia's death, some degree of Soviet foreknowledge or complicity might be assumed, though not necessarily at a high level in the Soviet chain of command on Afghanistan.
While the Soviet withdrawal from Afghanistan has been proceeding roughly on schedule, Soviet troops have recently launched offensive operations in areas they had vacated, according to US officials. For example, a Soviet pilot was shot down just inside the Pakistani border.
American officials were reluctant to discuss the possibility of Soviet involvement in Zia's death because of the high sensitivity of the subject and the potential for serious damage to US-Soviet relations, which have been in a warming phase.
A second possible group that might have sabotaged Zia's plane is Al-Zulfikar, the official said. The movement was dedicated to overthrowing the late President. The leader of the group is Murtaza Bhutto, son of the late prime minister, Zulfikar Ali Bhutto. Mr. Bhutto has headquarters in Kabul, the Afghan capital, and is also reported to have links to Syria and Libya. In 1984, Bhutto and his now deceased brother, Shahnawaz, were convicted in absentia in Pakistan for involvement in the 1981 hijacking of a Pakistan International Airlines flight.
According to the Pakistani official, the group has made other attempts at sabotage in Pakistan in an effort to weaken Zia's rule.
Bhutto's sister, Benazir, heads the main opposition party in Pakistan.
The third possible suspect, neighboring India, has a long history of hostility with Pakistan. India has long accused Pakistan of fomenting Sikh unrest in India's border state of Punjab.