Mayor Michael R. Bloomberg (R) apologized Monday for an incident in which heavily armed police ordered 60 tourists off a sightseeing bus and detained them for 90 minutes while checking out what he called an erroneous report of five suspicious passengers with backpacks.

"While we say call the professionals, call 911 or 311" -- the emergency and non-emergency phones numbers -- "you also have to exercise some common sense," Bloomberg said at a news conference. "These half a dozen people did not present any threat whatsoever, and it's a shame, and I certainly apologize on behalf of the city."

New York increased police protection of transportation facilities after the London public transit bombings.

When a Gray Line Bus Tour supervisor reported that five men carrying stuffed backpacks had boarded a double-decker tourist bus, a police captain summoned the city's heavily armed Emergency Services Unit, Deputy Police Commissioner Paul J. Browne said. Police ordered riders to get off with their hands in the air, patted them down and searched their bags while 51st Street between Eighth and Broadway was cordoned off.

Officers briefly handcuffed the five South Asian men who had aroused the suspicion of bus company employees. They did not have backpacks, Browne said. "After we determined that no one on the bus constituted a threat, everybody was released," he said. "The responding officers showed the appropriate caution in light of the information and the situation."

The mayor agreed. "The police didn't have any option other than to go and, based on what the tour operator reported, make sure they took total control of the situation right away with a large amount of force," Bloomberg said.

Cristyne Nicholas, president of NYC & Co., the city tourism and convention bureau, said she did not think the incident would hurt the city's hospitality industry, which generates about 300,000 jobs and $24 billion for the local economy.

"If anything, I think people are glad the caution is there," Nicholas said. "We have been told that 'when you see something, say something,' and to err on the side of caution. The company's first consideration was for their passengers and their city. I don't fault that."

Officials of Gray Line, part of London-based Stagecoach Group PLC, were unavailable for comment.