A Spirit Airlines flight preparing for takeoff at BWI Thurgood Marshall Airport returned to the gate just as it was taxiing to take off Tuesday.

Maryland Transportation Authority Police 1st Sgt. Jonathan Green said the Spirit flight No. 969, which was headed for Chicago, returned to the gate around 6:30 a.m. due to concerns from the flight crew. The flight was scheduled to depart BWI at 6.

Green said four people were removed from the plane for questioning.

There is no word on what concerns led to the plane returning to the gate or why the passengers were removed.