A Muni bus kept driving this morning even as passengers yelled from the back of the bus that the vehicle had struck a bicyclist on Market Street, witnesses and a Muni spokesman said.

A rider on the 5-Fulton bus said she heard a thump and then yelling as the bus headed east on Market near Fifth Street at about 8:30 a.m.

"People on the back of the bus said, 'You need to stop the bus! You need to stop!' " said Mary Chanzey. "(The driver) wouldn't stop, which I think is really crazy."

Judson True, a spokesman for the Municipal Transportation Agency, said initial reports were that the cyclist fell and "the bus then ran over the front wheel of the bicycle." There was no indication that the bus hit the cyclist, he said.

But the driver should have stopped, True said.

"It is clearly the policy that if an operator is informed of a possible collision, that he or she should stop the vehicle and call central control," True said. "We received a report from another bus of a bicyclist down."

The 5-Fulton driver did pull over briefly past the crash and told passengers that the bicyclist had fallen by herself, Chanzey said.

The bicyclist was conscious and appeared to have a scrape on her head as she was loaded into an ambulance in a neck brace. Her injuries are not believed to be life-threatening, True said.

The driver's name has not been released. Muni officials and police were investigating the incident and interviewing the driver.