(Reuters) - The Federal Aviation Administration on Monday was investigating a collision between a Southwest Airlines Co aircraft and a truck at Baltimore-Washington International Airport as the airline faced scrutiny over a midair engine explosion last month that killed a passenger.

The FAA said it is investigating after Southwest Airlines jet and a truck collided as the Boeing 737 pulled into a gate at about midnight. Passengers got off the plane using air stairs that are pulled to the aircraft, the aviation safety agency said.

Southwest Flight 6263 was pulling into the gate at BWI Sunday evening after flying from Ft. Lauderdale, Florida, “when a ground vehicle came into contact with the aircraft,” the airline said.

There were no injuries reported to the 172 passengers aboard, the FAA said.

“As with any event, we will conduct an internal investigation to learn what happened in the interest of safety. It would be irresponsible to provide details until we’ve had time to thoroughly review the facts,” Southwest spokeswoman Michelle Agnew said.

An engine exploded during a Southwest flight last month that killed a passenger, the first on a U.S. carrier since 2009.

Southwest shares were down 1.2 percent at $52.19, extending a 20.1 percent year-to-date decline.