Officials say they temporarily grounded air tankers for safety reasons after a hobbyist's drone flew near a huge forest fire in Southern California.

Daniel Berlant of the California Department of Forestry and Fire Protection says a tanker was preparing to drop retardant Wednesday evening in the San Bernardino Mountains when the pilot spotted the small remote-controlled device.

Officials ordered him and four other pilots to land over fears of possible collisions, but they were unable to find the drone's operator.

Berlant says a short time later, the pilot of a spotter plane saw another small drone flying over a different section of the fire.

Retardant-dropping flights resumed Thursday.

The blaze about 90 miles east of Los Angeles has charred 33 square miles of timber and brush since June 17.