PORTSMOUTH, New Hampshire — A passenger on a Maine-to-New York Greyhound bus surrendered to authorities Thursday night after a nine-hour standoff sparked by a bomb scare.The man walked off the bus with his hands up and got to his knees. He then walked away from the bus, apparently following orders from police.The 16 other passengers and driver on the bus, which was surrounded by a bomb squad and sharpshooters, including one in an armored vehicle, had been removed hours earlier.The ordeal began Thursday morning, when one of the passengers called police to report an explosive device on board.The emergency call came after the bus arrived in the seaside city of Portsmouth around 11:30 a.m. and was "based on someone's observations," police Capt. Mike Schwartz said. It was unclear which passenger made the call.Greyhound spokeswoman Maureen Richmond said the driver properly parked and secured the bus and got out. Police surrounded the bus and evacuated nearby buildings and streets.The passengers were on the parked bus for more than two hours before police started calling most of them out under the watch of a sharpshooter. They left the bus separated by a couple of minutes each and carried no purses or bags. Most held their hands aloft as they passed officers with their weapons drawn.The passengers were screened individually when they got off the bus — much like an airport security check — and were taken to the Portsmouth police station. None appeared to be injured as they left the bus; Schwartz said one was taken to a hospital because of a medical condition.The last man, who police said was wearing camouflage pants, remained aboard and communicated with police during the standoff.Some of the other passengers finally resumed their trip on a replacement bus just before 8 p.m., more than an hour after the original bus had been scheduled to arrive in New York City.