A pedestrian was hit by a car and critically injured in Prince George’s County on Saturday in what authorities think may have been the second case in less than 24 hours of death or serious injury in the county resulting from street racing.

In Saturday’s incident, a 21-year-old man was found lying in the 2000 block of University Boulevard in the Langley Park area about 3:15 p.m., the county police said. He was not in a crosswalk when he stepped into the road and was hit, police said.

They said the car that hit him continued east on University Boulevard without stopping.

A preliminary investigation indicated that car’s driver and a second vehicle were seen nearby racing near University Boulevard and Riggs Road, police said.

On Friday night, the driver of a car was fatally injured about 9:30 p.m. when his vehicle collided with a Metro bus in the Seat Pleasant area, the police said.

They said speed was apparently a factor in that crash, which killed Cleon David Wills, 22, of Bowie.

They said they thought that he was racing another car at the time of the collision with the bus near Central Avenue and Soper Lane. Eight passengers on the bus were sent to the hospital with minor injuries.

Neither of the areas where the incidents occurred were known for street racing, police said. They said they will monitor major thoroughfares for such activity.