Maryland ? A commercial helicopter crashed onto a western Maryland highway and burst into flames late Thursday night, killing all four people on board, emergency officials said.

The aircraft was engulfed when firefighters arrived at the scene minutes after receiving a call at 10:30 p.m., said Washington County emergency services director Kevin Lewis. No vehicles on the highway were hit when the helicopter crashed in the eastbound lanes of Interstate 70.

Troopers have shut down the highway in both directions near the crash site. Lewis, who was among the first emergency responders at the scene, said there are power lines down in the westbound lanes.

It wasn’t immediately clear what brought down the helicopter, which Lewis said was a Robison R44, a four-seat commercial craft.