Firefighters responded to a four-alarm fire Tuesday in northwest Houston. The Gentry House Apartments at 9001 Kempwood Drive caught fire at about 5:30 p.m. The fire was declared under control at about 8:15 p.m. The cause of the fire is unknown and it remains under investigation by the Houston Fire Department’s arson bureau. The Red Cross will be assisting residents displaced by the fire. There was little time to react for residents as flames washed over four buildings within minutes.