BROOKLYN - Investigators are trying to figure out what caused two vacant Coney Island buildings to go up in flames overnight. 

Officials say the three-alarm fire started inside a three-story building on West 19th Street at around 2 a.m.. It quickly spread to the top floor and over to another building. 

According to neighbors, the two buildings have been empty since Superstorm Sandy. 

Firefighters had the blaze put out at around 3:30 a.m., and no one was hurt.