Five workers were killed in Far East Russia’s Zabaikalsky region when an all-terrain vehicle carrying nine people plunged into a remote mountain lake earlier this week, emergency officials said.

Nine employees of a local geological exploration company were on a fieldwork assignment when a suspected brake failure caused their tracked all-terrain vehicle to sink into Lake Amudisa on Monday.

Four survivors notified authorities of the incident after reaching a populated area on Tuesday.

Three bodies were retrieved on Wednesday, and the other two later on Thursday. Emergency authorities said they were planning to use heavy machinery to pull the vehicle from the water.

Police investigators launched a criminal case into safety violations without indicating whether any arrests were made.

Three of the victims were identified as employees of an unnamed commercial organization, and two others as security guards.

An unverified report identified the survivors as two geophysicists and two drivers.

Russian news agencies reported that the fieldwork assignment was performed on behalf of Hydrostroy GeoTech, a local geological and geophysical survey company that operates in Siberia and Far East Russia.