A pipe bomb exploded on a police vehicle in suburban Maryland early Wednesday, the police said.

The vehicle was parked on the street outside an officer's house in Thurmont, Maryland, Police Chief Greg Eyler told CBS Washington, D.C., affiliate WUSA-TV.

At around 12:30 a.m., the officer heard an explosion, Eyler told WUSA-TV. He and his wife went outside, and they found the remains of a pipe bomb beside his vehicle.

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Eyler said it looked like someone placed the pipe bomb on the hood of the vehicle against the windshield. The main damage to the vehicle was to the windshield, and the bomb also blew out at least one side window.

The explosion sent shrapnel into a nearby house, sources told CBS News homeland security correspondent Jeff Pegues.

No one was injured, Eyler said.

A source told CBS News the bomb was "legit."

The bomb fragments were being analyzed at a lab for the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, Pegues reports.

No one was under arrest and the motive was unclear.

Investigators were not ruling anything out because of recent incidents where police officers have been targeted, Pegues reports.