LONDON — Emiliano Sala, the Argentine soccer player who died in a plane crash in the English Channel in January, had been exposed to “potentially fatal” levels of carbon monoxide, the British authorities revealed on Wednesday.

Mr. Sala, 28, who was on a flight from France to Wales on Jan. 21 when the aircraft went down, sustained carbon monoxide poisoning in the cockpit of the plane, according to a report released by Britain’s Air Accidents Investigation Branch as part of its inquiry into the crash.

Toxicology tests on Mr. Sala’s blood revealed that he had been exposed to the odorless, colorless gas at a high level that “in an otherwise healthy individual is generally considered to be potentially fatal,” according to the interim report, or special bulletin.

Mr. Sala’s body was not recovered until February. The body of the plane’s pilot, David Ibbotson, has not been found, but investigators concluded that he would most likely have been affected by carbon monoxide exposure.