(CNN) Australia's busiest airport was on high alert Thursday after a United Airlines flight from Los Angeles issued a mayday call due to low fuel reserves.

Police said they activated a "full emergency response" after the pilot of flight UA839 reported a problem around 6 a.m. local time. Some major roads around the airport were briefly closed "as a precaution" as the plane made its final approach.

In a statement, United said the flight experienced a "mechanical issue," adding that it "taxied to the gate and all customers disembarked normally."

Airservices Australia, the nation's navigation authority, said the pilot issued a mandatory mayday call due to low fuel levels as the flight completed its 15-hour trip from LAX.

"A fuel mayday triggers emergency procedures," a spokeswoman said. "This was a precautionary procedure and at no time were the passengers at risk."

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