LOS ANGELES (CBSLA.com) — Authorities have issued a warning to the public Friday after they say two flying drones disrupted wildfire operations in Southern California this week.

The first drone was spotted Wednesday and prompted firefighters to suspend airtanker operations over the Lake Fire burning south of Big Bear Lake that has scorched more than 17,000 acres.

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The following day, authorities say a two other drones were spotted over the 100-acre Sterling Fire in San Bernardino, temporarily halting tanker operations. According to the U.S. Forest Service, one of those drones interfered with firefighters’ operations, while the second had not.

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Because airtankers have to fly at low altitudes, there exists a possibility for a mid-air collision with a drone, the National Interagency Fire Center said in a written statement.

“If a UAS is detected flying over or near a wildfire, we will stop airtankers from dropping fire retardant, helicopters from dropping water, and other aerial firefighting aircraft from performing wildfire suppression missions until we can confirm that the UAS has left the area and we are confident it won’t return.

“Unfortunately, this could decrease the effectiveness of wildfire suppression operations, allowing wildfires to grow larger, and in some cases, unduly threaten lives and property, but firefighter and public safety are our top priorities in wildfire management,” said Steve Gage, a U.S. Forest Service representative.

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Civil penalties and even criminal prosecution may result, authorities say, if it’s determined that a person has interfered with firefighting efforts.