The singer was not on the bus at the time and performed later that night at Joe Louis Arena in Detroit.
Hammond says a police dog indicated the presence of drugs on the bus and that drug paraphernalia and a small amount of marijuana were found. He says the bus driver was cited and that the bus and its passengers were allowed to go.
Meanwhile, German authorities have posted a public notice urging Justin Bieber to get in touch with them about an unpaid bill for his former pet monkey Mally.
Bieber failed to produce the necessary vaccination and import papers for the monkey when he arrived for a European tour in March. Mally became the property of the German government in May when the Canadian singer failed to claim his pet.
A spokesman for the Federal Agency for Nature Conservation says Bieber has one week to pay 1,130 euros ($1,500) for the monkey's care.
Franz Boehmer said Tuesday that otherwise customs officials "have ways of making him pay" next time he enters Germany.
Bieber is already on the hook for a separate 5,000-euro bill from Munich customs.