A blood clot caused the death of a South African woman on board a Via Rail train last week in an incident that sparked a full-scale health scare.

Dr. William Lucas, with the Ontario Coroner's Office, told The Canadian Press Monday that 43-year-old Brenda Buckley died of a pulmonary embolism.

The condition occurs when an artery in the lung becomes blocked. The blockage is generally caused by one or more blood clots that travel to the lungs from another part of the body.

Lucus could not confirm reports that the clot was the result of deep-vein thrombosis -- which can develop when people sit for long periods of time. He did say, however, it was a likely cause.

Buckley died on the train, which was travelling from Jasper, Alta., to Sudbury, Ont. on Friday. The train was stopped and quarantined about 100 kilometres west of Timmins, Ont.

Catherine Kaloutsky, a spokeswoman for Via Rail, said Monday that no one has ever died from deep-vein thrombosis on one of Via Rail's trains.