On March 23, before the next mission, an accident occurred during training which led to the death of cosmonaut candidate Valentin Bondarenko. He was burned in a fire in an oxygen-rich isolation chamber, and died in a hospital eight hours after the incident. Bondarenko's death was the first known cosmonaut or astronaut fatality. It is not clear whether other cosmonauts were told of his death immediately; the media did not learn of Bondarenko's death – or even of his existence – until many years later, in 1986. Unsubstantiated reports of other cosmonaut deaths created the myth of the lost cosmonaut.