Two Marines were badly burned during what US Marine Corps officials are calling a 'ground flash fire' on Sunday night.

The Marines were engaged in routine aircraft maintenance on a F/A-18 Hornet fighter jet at the Marine Corps Air Station Miramar in San Diego, California at about 10.18pm when the fire started, according to a media release from the base's public affairs office.

The two injured Marines were taken to UC-San Diego Regional Burn Center for treatment of their severe burns. A spokesperson told the Marine Corps Times that one of the Marines is in critical condition.

Two Marines from Marine Fighter Attack Squadron 112 were badly burned during a 'ground flash fire' while performing maintenance on a F/A-18 at Miramar airfield in San Diego, California

The ground flash fire took place at 10.18pm on Sunday at Marine Corps Air Station Miramar in San Diego, California (pictured). One of the Marines is in critical condition, authorities said

Marine Corps officials initially described the incident as having been an 'explosion,' but later amended the statement to reflect that it was actually a 'ground flash fire' that had occurred. The incident is under investigation.

Flash fires — a sudden and intense fire — typically happen when flammable substances, such as jet fuel, mix with air.

The San Diego area is currently experiencing its second major heatwave this month, with inland temperatures reaching in the 100s, according to The San Diego Union-Tribune.

The injured Marines belong to Marine Fighter Attack Squadron 112, a reserve unit based out of Fort Worth, Texas.

Air Station Miramar currently houses the 3rd Marine Aircraft Wing.

The Miramar airfield gained international recognition in the '80s — back when it was known as Naval Air Station Miramar — for housing the United States Navy Fighter Weapons School, which inspired the movie 'Top Gun.'

During an interview in May with Sunrise, Tom Cruise revealed that a 'Top Gun' sequel is officially in the works and is expected to begin filming in 2018.