Some 13 workers on the Channel Tunnel were intoxicated by carbon monoxide poisoning on Sunday night – the second such incident to occur within 24 hours.
Reports of the second incident come after 19 people were hospitalised overnight on Saturday after working in the tunnel that links Calais in France to the town of Folkstone in Britain.
In the second outbreak of poisoning 65 workers had to be evacuated in total for safety reasons with 13 admitted to hospital for tests, French newspaper La Voix du Nord reported on Monday.
On Saturday 60 people, including workers from a company commissioned by Eurotunnel and Eurotunnel employees, were in the process of changing rails on the line between the towns of Calais in France and Folkestone in Britain when a welder took ill overnight Saturday, said officials from France's Pas-de-Calais department.
"Carbon monoxide poisoning was diagnosed," an official said, adding the worker, who was "quite seriously affected", was taken to a hospital in Calais then Lille in northern France.
Eighteen other workers were also taken ill and sent to hospitals in Calais, Boulogne-sur-Mer and Dunkerque, "the time needed to remove the carbon monoxide from their system", an official said, adding their condition was not a cause for concern.
The 41 other workers were able to return home.
An investigation had been launched into the cause of the incident. Train traffic through the tunnel has not been affected by the incidents.