A single-engine An-2 biplane that went missing in the Urals on Tuesday and had not been found by Wednesday evening was carrying the local traffic police chief and possibly several other police officials, investigators said Wednesday.
The plane, which police said belonged to Chelyabinsk-based carrier Avia Zov, took off from a small airstrip near the city of Serov at 11 p.m. Monday without permission from air traffic controllers, Interfax reported.
By Wednesday evening, investigators had established the identity of some of the passengers but had still not found the missing craft.
Aside from the plane's captain and a security guard for the airstrip, at least six people were aboard the missing plane, including top local traffic cop Dmitry Ushakov and a traffic police officer, the Investigative Committee said in a statement.
Valery Gorelykh, a spokesman for the regional police, had earlier estimated that there were as many as 12 passengers on the biplane.
Eyewitnesses speculated that relatives of local police also had been on board the An-2, the Investigative Committee statement said.
Investigators responded by mobilizing two aircraft and a helicopter to search for the plane. Seventy-three Sverdlovsk police officers, seven Emergency Situations Ministry personnel, and local transportation prosecutors were also added to the search party.
Investigators are conducting a probe with a charge of violating flight-safety rules leading to the death of two or more people through carelessness.
Other scenarios, including a technical malfunction, theft of the plane and taking off in unsafe weather conditions, are being considered, according to investigators.
The co-pilot and flight engineer first found the plane missing Tuesday morning when they returned from a brief visit to Serov, an industrial city of 100,000 people located 350 kilometers north of Yekaterinburg.
They also found three abandoned cars near the spot where the plane had been parked before alerting police at 8:30 a.m. Tuesday.
Police are still confused as to why the plane took off.