Three tour buses parked in front of a Hilton hotel in Arlington, Va., were engulfed in flames Friday morning after they mysteriously caught fire, MyFOX D.C. reported.

Authorities are investigating the fire, which sent thick, heavy smoke into the hotel, causing 150 guests to be temporarily evacuated, according to The Washington Post.

No injuries were reported and the cause of the fire is unknown.

"Our first concern is always just guest safety," Hilton Crystal City Hotel general manager Ben Thompson told the Post. "And all the guests were fine. Everybody was safe, nobody was hurt."

The burned buses were those of tour groups staying at the hotel. The tours were able to continue sightseeing after new buses arrived to replace those gutted by the flames.

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