An unidentified woman was struck and killed by a Maryland Transit Administration bus yesterday morning in Fullerton, police and MTA officials said.

The No. 55 bus on the Fox Ridge-to-Towson University route was heading west on Fullerton Avenue and made a left onto Belair Road heading south "when the six passengers aboard said they heard a thump," said MTA spokesman Richard E. Solli.

"The bus operator immediately stopped. When they looked behind them, they saw a woman lying in the street," Solli said.

By the time emergency medical crews arrived minutes later, Solli said, the woman had died.

A Baltimore County dispatch officer said police could not comment while the investigation was pending. Authorities said the victim was white, in her 40s to 60s, about 5 feet 1 inch tall with a medium build, and had no identification.

Following procedure after a collision, the driver was tested for drug and alcohol use and placed on "nondriving status" pending the investigation, Solli said.