A biplane vanished from an airfield in the Ural mountains, apparently stolen by the pilot and his drinking buddies for a fishing trip or a visit to the bathhouse, investigators said on Tuesday.

The An-2 biplane, which was tasked with monitoring wildfires, departed from an airstrip near the town of Serov in Sverdlovsk region on late Monday without contacting the air control, the Investigative Committee said in a statement.

The disappearance was reported by the second pilot and the flight attendant who took a short trip to Serov, returning to find the aircraft gone, the report said.

Three cars were left at the airfield, the committee said, without identifying their owners. At least seven people, including pilot Khatib Kashatov and an unnamed airfield guard, may be on board, regional police said.

The men were apparently drinking and decided to go fishing or fly someplace to visit a banya, a type of Russian steam bath, police said.

Search for the plane was ongoing on Tuesday evening, with people alleged to be on board not returning calls to their mobile phones, investigators said.

Photo: Rob Vogelaar Z.A.P.P.