Investigators work at the site of a holicopter crash in the Krasnoyars region, Russia on August 4, 2018. (Photo by Russian Investigative Committee)

MOSCOW, Aug. 4 (Xinhua) -- A helicopter crash in Russia's Krasnoyarsk region in Siberia killed all 18 people on board on Saturday, the Russian Emergencies Ministry said.

The accident took place at 9:48 local time (0248 GMT) when an Mi-8 helicopter crashed 180 km north of the town of Igarka in Turukhansky District, the ministry's Krasnoyarsk region branch said in a statement.

None of the 15 passengers and three crew members on board survived, the ministry said.

All the passengers were reportedly staff members of a subsidiary of the Russian state oil company Rosneft.

According to preliminary data, the helicopter belonging to Russia's UTair airline collided with the external cargo suspension of another helicopter that took off earlier, before it fell, collapsed and burnt, a statement published by Russia's Federal Air Transport Agency said.

The helicopter with cargo carrying no passengers landed safely after the crew dropped the external suspension, it added.

The acting governor of the Krasnoyarsk region Alexander Uss declared August 6 the day of mourning for the victims of the plane crash, the regional government's spokeswoman Elena Ulyasheva said.

The head of the region has also instructed relevant government bodies to make arrangements to meet and accommodate the victims' relatives with necessary psychological and medical care, as well as to work on the issue of providing financial assistance to the families of the victims.

A task force was set up to establish the causes and conditions of the catastrophe, and the criminal investigators of Russia's Investigative Committee were sent to the scene, the committee said in a statement.

The investigators are checking the flight documentation, taking fuel samples and interrogating maintenance personnel, employees of the airline and witnesses of the crash, the committee said.

All possible causes of the crash are under consideration, including the possibility of a pilot error, but final conclusions can be reached only after the investigations and examinations, it added.

Both black boxes of the helicopter have been found, a source in regional emergency services was quoted by Sputnik news agency as saying, adding that the recorders are in a satisfactory condition.

The flight data recorders will be sent to the Interstate Aviation Committee in Moscow for possible decoding, according to a source in law enforcement bodies.

The Russian Emergencies Ministry is sending over a group of An-74 and Be-200 aircraft and a total of 25 people from regional search and rescue centers to the site of the crash, according to the Krasnoyarsk region branch of the ministry.

Currently, a total of 75 people and 8 units of equipment, including 38 people from the Emergencies Ministry, are working at the scene of the crash to eliminate the consequences, it added.