Pilot error, technical malfunction and bad weather are all possible causes checked by investigators.
Putin fires top official in Russian Far East, and calls for Investigative Committee to check how authorities performing.
Average temperatures in the north of the Kara and Barents seas were 4C to 5C higher than previous years.
Warnings of worse rain for the rest of the week came on Wednesday as evacuation of 30 settlements was planned by the authorities.
Huge damage wrought by forest fires is sparked by failure to apply safety laws, complained Yuri Chaika.
Locals get time off week for rare visit to the beach.
Summer flooding will worsen dramatically, and the Arctic could be ice-free in summer by 2034.
Forest infernos will be extinguished by the weekend, pledges government, as wildfires become political issue in Moscow.
Prime Minister's eastern promise of special incentives for entrepreneurs.
Putin backs proposal to give one hectare to each citizen or person willing to move to region in a bid to stimulate economy and boost population.