Eight people including at least two children were killed Sunday and a ninth person feared dead after a mid-air collision between a helicopter and a light aircraft in the Moscow region.
Investigators said Sunday that pilot error was the likely cause of the fatal accident, which occurred at around 8:20 p.m. the day before over the Istra reservoir to the northwest of the Russian capital.
Four people were flying in the helicopter, a Robinson 44, and five people were in the seaplane, a Cessna-206, when the two aircraft collided in mid-air about 500 meters from the shore, according to news agency Interfax.
The remains of both aircraft fell into the water after the accident, where they sank to a depth of 13 meters.
"The working hypothesis is that it was pilot error … investigators are now building up a picture of events using witness testimony," local investigator Tatyana Morozova was cited as saying by the TASS news agency.
The pilot of the seaplane, who reportedly flew people around the area for a living, was in the air without official permission, Interfax reported, citing an unidentified source in Russia's Federal Air Transportation Agency.
Eight bodies had been recovered from the reservoir by Sunday evening, according to the head of the Istra district administration, Interfax reported, citing local television.