Crews increased containment while halting the growth of a wildfire burning in rugged land at a central California military base, authorities said Thursday.

The blaze at Vandenberg Air Force Base was 70 percent contained, and base officials said they were hopeful that number would go up throughout the day.

The fire that broke out in a remote canyon and forced the postponement of a satellite launch was holding steady at about 19 square miles after several days of growth.

There was no word of any threatened structures on the sprawling base, much of which is undeveloped mountain land. The cause was under investigation.

A firefighter died Wednesday and another was hurt when the water truck they were in overturned on a highway outside the city of Lompoc, miles from the fire lines.

Ventura County firefighter Ryan Osler was killed, and Adam Price was injured. There were no other occupants in the truck.

The California Highway Patrol was investigating the cause of the crash.

Officials said the fire did not pose an immediate threat to the base's launch complex that fires satellites into space.

Vandenberg encompasses nearly 156 square miles (405 sq. kilometers) along the Pacific Ocean. A wind-whipped fire in 1977 killed the base commander, the base fire chief, an assistant chief and a bulldozer operator.