PORTLAND – A 19-year-old man was jailed Friday after 10 cars were set on fire near downtown before sunrise, with three fires spreading to nearby apartment houses, police said.

Thomas Cassidy of Portland was being held on $250,000 bail on single counts of arson, breaking into a motor vehicle, and carrying a concealed weapon.

Cassidy is a suspect in all the fires, police said. Nobody was injured.

The first call came in about 4 a.m. for a car fire outside an apartment house on Sherman Street. The fire spread from the car to the building, forcing more than 20 people to evacuate.

In the next two hours, firefighters were called to nine other fires in a roughly 10-block area, where they found cars – one after another – engulfed in flames in the Parkside and West End neighborhoods.

The cars were parked on streets and in parking lots and driveways and were set on fire with an accelerant, Police Chief Tim Burton said.

In three of the fires, flames spread to nearby apartment houses. The building in the first fire was extensively damaged, but damage was confined to the exterior of the other two buildings.

Cassidy was stopped at about 6 a.m. down the street from one of the fires. Burton did not know if Cassidy had a job or where he grew up, and said he was a “floater” who was living among friends’ places in Portland.

Burton did not elaborate on a motive, but said the fires appeared to be randomly set.

“Right now there’s no discernible pattern … to the cars that were chosen,” he said.

Police also received nine reports of vehicles being vandalized or broken into in the same area, with tires slashed, paint damaged and small items taken.

The State Fire Marshal’s Office and the federal Bureau of Alcohol, Tobacco and Firearms were assisting in the investigation.