A woman and two young children were found dead Monday afternoon in a car in a parking lot at a school in Hagerstown, Md., authorities said.

No names were available for the three as of late Monday, and there was no immediate indication of a cause of death for any of them. No obvious signs of violence were found, authorities said.

The children were described as apparently too young to walk by Sgt. Chris Barnett of the police in Hagerstown, a city of about 40,000 about 60 miles northwest of the District.

About 4 p.m., police were sent to a parking lot at Western Heights Middle School, part of the Washington County school system, according to a statement from the city that was released by Mayor David S. Gysberts.

The city’s statement said authorities had received a call about a woman and two children who were in a vehicle and appeared to be unresponsive.

The woman was found in the front seat of a small, silver-colored vehicle.

Two children were in the back seat. All were dead, the city’s statement said.

Barnett said surveillance footage would be checked to determine when the car entered the lot. He said he understood that the vehicle doors were unlocked when police arrived. The last day of school in the county was Thursday.

The school, just northeast of Interstate 81 and U.S. Route 40, is surrounded by a broad expanse of grassy playing fields. The parking lot is not readily visible from surrounding streets and roads.