Nineteen workers who were part of a team changing rail tracks in the Channel Tunnel have suffered carbon monoxide poisoning. One of the workers is in a serious condition.

A welder on the team, which was working overnight, took ill in the early hours of Sunday 26 January and was later diagnosed with carbon monoxide poisoning. Eighteen other workers then fell ill and were sent to local French hospitals. An official has said their stay in hospital is necessary in order give them “the time needed to remove the carbon monoxide from their system”. The other workers in the team were subsequently sent home.

It is, however, unclear as to the cause of the poisoning. John Keefe, director of public affairs at Eurotunnel Group, said “Detectors in the tunnel didn't show excess levels of carbon monoxide. A number of workers were taken into hospital for medical observation as a precaution and Eurotunnel is monitoring their condition carefully.”

An investigation has now been launched into the cause of the carbon monoxide poisoning.