A massive fire broke out early Tuesday morning, engulfing the historic north blimp hangar in Tustin, Orange County. The hangar, which dates back to World War II, was one of two constructed by the military for the Tustin Naval Air Station.

The fire was so intense that helicopters were deployed to drop water on the structure, according to the Orange County Fire Authority. Due to the danger of collapse, firefighters made the decision to let the flames weaken the mostly wooden hangar before intervening.

Constructed mainly from Oregon Douglas fir, each hangar measures at least 17 stories high, 1,088 feet long, 297 feet wide, covering nearly 300,000 square feet. They are considered among the world's largest free-standing wooden structures and were listed in the Register of National Historic Places.

These hangars housed 12 blimps during WWII, armed with machine guns and bombs for submarine patrol. Plans to convert the site into a regional park had been abandoned in 2021, following concerns about structural damage.

Firefighters are still battling the blaze, which has raised concerns that the hangar may completely collapse. The cause of the fire remains unknown.