Two Port Authority bus operators have been cited for careless driving in connection with recent crashes.

Two other accidents, one of which killed a 79-year-old man on Sunday, remain under investigation, Port Authority spokesman Jim Ritchie said yesterday.

The police investigation of a fifth accident, in which a bus drifted backward into a retaining wall in North Braddock, injuring 13 passengers, resulted in no charges against the driver, he said.

Mr. Ritchie said it was unusual for the authority to have so many accidents in less than a month.

"In some cases, the investigation shows that our drivers did something that wasn't by the book. When that happens, they're cited or something is done internally," he said.

Robert Clark, 59, an authority employee since 1994, was cited for careless driving and failure to yield in a May 21 collision with a bicyclist at Forbes and Murray avenues in Squirrel Hill.

Rose Marie Berkavich, 49, with the authority since 1999, was cited for careless driving in a May 29 crash into a utility pole at Baum Boulevard and North Craig Street in Oakland. Nine passengers were hurt.

On June 3, a 68D Braddock Hills bus drifted backward into a retaining wall at Brinton Avenue and Corey Street in North Braddock.

After an investigation, no charges were filed against the driver, Dashoka Davis, 39, an authority employee since March.

Mr. Ritchie said he could not comment further on that case because of the likelihood of litigation. He also said he could not divulge details about any possible internal discipline involving the drivers who were cited in the other crashes.

In the latest accident, Henry Glasgow, 79, of Wilkinsburg, had gotten off the bus at the Swissvale station on the East Busway shortly before 6 p.m. Sunday, but decided to get back on as the bus pulled away. He fell and was run over by the rear wheels. He was pronounced dead at 7:10 p.m. Sunday at UPMC Presbyterian.

The driver, Blanche Rankin, 44, hired in 2000, is on leave during the investigation.

On June 1, a man was seriously injured after falling under a bus while chasing it near Liberty and Seventh avenues, Downtown.

Witnesses said the man ran behind the bus and then alongside it, banging on the side. He fell under the bus and was dragged several feet. The driver, Leonard Patterson, 53, an employee since 2005, also is on leave pending the outcome of the investigation.

Mr. Ritchie said there was "no common thread" to the recent accidents and that riders should not be alarmed.

"Riding a bus and being safe about it has a lot to do with common sense," he said. "You shouldn't chase after or run alongside a bus while it's moving or bang on the door."