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CAMP PENDLETON, Calif. — A brush fire that spread across swaths of open terrain on the grounds of Camp Pendleton late Thursday afternoon is now 75% contained, a spokesperson from Camp Pendleton Media Relations said.

The blaze broke out in the eastern reaches of the sprawling Marine Corps installation and had scorched about 80 acres as of shortly after 5 p.m., but no structural threats were reported, base officials said.

By 7 p.m., the fire had burned about 120 acres and was 40% contained, according to Cal Fire Public Information Officer Thomas Shoots, who said fire activity had “decreased significantly” as nightfall approached with full containment expected by midnight.

Just before 7 a.m., Cal Fire tweeted that the fire, which didn’t exceed 120 acres burned, had been 100% contained. An hour later, Camp Pendleton Media Relations said they could only confirm that 75% of the fire was contained at 120 acres burned.

Civilian firefighters were helping military personnel extinguish the blaze, according to Cal Fire. Shoots said 75 firefighters were deployed.

The cause of the fire was not immediately clear.