San Diego Zoo Safari Park entrance.

A fire of unknown origin burned swaths of brushy terrain Monday on a hillside near the San Diego Zoo Safari Park, but there were no reports of structural threats.

The blaze erupted near Bandy Canyon and Old Survey roads in the San Pasqual area shortly before 1:30 p.m., according to the San Diego Fire-Rescue Department.

Within an hour, the fire had blackened roughly 12 open acres as ground crews and personnel aboard air tankers and water-dropping helicopters worked to halt its spread, said SDFRD spokeswoman Monica Munoz. As of 2:45 p.m., most of the flames had been snuffed out.

It was not immediately clear what sparked the blaze.

— City News Service