CAMP PENDLETON --  A brush fire spread through an open training area at Camp Pendleton today, sending smoke over northern San Diego County but causing no structural threats.

The blaze erupted for unknown reasons in the late afternoon and was charring light vegetation in a remote locale toward the middle of the sprawling Marine Corps station, base fire inspector Bill Gick said.

Because the flames were nowhere near developed land on the military installation, the Camp Pendleton Fire Department was not working to extinguish them, but instead was "just monitoring the situation," Gick said.

"We just kind of let (this type of fire) take its own course, burn itself out," he explained shortly before 6 p.m. "There are no heavy fuels out there."

Gick said he did not know the size of the burn area.