Mexican San Diego Fire 051712

A 600-acre brush fire that has been burning in Mexico since Wednesday crossed into San Diego County, where it burned about 15 acres Thursday, Cal Fire said.

The blaze spread across the border side between the communities of Boulevard and Jacumba, south of Boundary Peak near Jewel Valley, where Cal Fire firefighters responded about 8:30 a.m.

No structures were threatened as winds pushed the flames northeast. One firefighter suffered a heat-related injury, fire officials said.

The cause of the fire was unknown.

By mid-afternoon, four air tankers, three helicopters, and 200 firefighters had stopped the blaze. Fire engines and bulldozers worked just south of the border, to eliminate the threat to the U.S., Cal Fire spokeswoman Roxanne Provaznik said.

Crews were going to keep dousing hot spots overnight and monitor the fire as it continued burning toward the east in Mexico.

Cal Fire was assisted by the U.S. Forest Service, the Bureau of Land Management, Heartland fire agencies, the Sheriff’s Department and Border Patrol.