“Our stations are very busy today. Please don’t come to the station unless you have a valid ticket to travel,” officials warned.

The rail provider, which runs daily service through the English Channel tunnel between London’s St. Pancras Station and Gare du Nord in Paris, apologized for the “impact caused” as thousands of passengers stranded in London scrambled to change their plans.

British utility Thames Water later on Saturday revealed the problems were caused when a pair of railway tunnels running under the Thames River near Ebbsfleet International station in the county of Kent were flooded.

“We have been informed of an incident involving a pipe flooding the Eurostar tunnel. We believe the incident is in regard to a fire control system and not a Thames Water pipe/asset, however we have a technician on the way to offer support to control the flow of water,” the utility said in a statement issued to The Independent.

“We will continue to monitor the situation and offer support where needed.”

Also affected by the flooding is local service provided by Britain’s Southeastern Railway.

“Our high speed services are currently unable to operate due to ongoing flooding. Sorry if you are affected,” Southeastern Railway Managing Director Steve White said in social media post.

The provided had “no timescale for resolution,” noting that the flooded tunnel is owned and operated by High Speed 1, the 67-mile rail line between St Pancras International in London and the Channel Tunnel.

The latest delays for Eurostar travelers came only a week after flash strike by French employees crippled the vital undersea rail link between France and Britain.