Eurostar — which runs passenger trains between London and Paris and other European destinations — blamed "overhead power supply issues in the Channel Tunnel" and a failure aboard a train operated by LeShuttle, which transports vehicles and their passengers between the ports of Calais, France, and Folkestone, England.

Traffic slowly resumed Wednesday in the Channel tunnel after an electricity failure halted train trips connecting London to the European mainland, as frazzled passengers arrived in France after hours trapped in a powerless train.

Eurostar has told passengers not to travel due to a “major disruption” in the Channel Tunnel, and to expect severe delays on trains booked for departure soon. A statement issued by the train service on Tuesday morning advises that a problem with the ...