A fire ripped through a three-story apartment building in Yonkers this morning, and police say a tenant has been arrested for sparking the flames with his illegal marijuana-growing operation. Officials say the fire erupted in a top-floor unit at 81 Van Cortlandt Park Ave. at about 8:15 a.m. It took a team of 70 firefighters to put out the fire. Investigators say a third-floor tenant was using high-powered heat lamps to grow marijuana inside his apartment. The lamps overloaded the electrical system, sparking the flames, police say. The suspect, whose identity has not yet been released, was arrested and remains in police custody. All 20 people who lived in the building escaped safely, authorities say. The Red Cross says it is assisting the victims in finding temporary housing.