NEWARK, N.J. (AP) — Two firefighters were killed battling a blaze that began when cars caught fire deep inside a cargo ship carrying 5,000 cars at a New Jersey port Wednesday night, Newark’s fire chief said.

Firefighters responded to a report of a fire in a cargo ship at Port Newark around 9:30 p.m. and found the fire involving five to seven vehicles on the 10th floor. The blaze quickly extended to the 11th and 12th floors, Fire Chief Rufus Jackson said at a news conference. Firefighters tried to extinguish the fire, but as they were pushed back by the intense heat and two firefighters were lost, he said.

Firefighters weren’t initially able to find their colleagues and outside rescue companies from around the state were called in. They were found and removed from the structure, but unfortunately they lost their lives, Jackson said.

“We lost two firefighters today,” said Newark Mayor Ras Baraka at the scene. “A tragedy for us in the city of Newark and tragic for all firefighters who know what it means to go in a burning structure in a danger that you are going to have to experience when you do so.”