French authorities have arrested a person inside the Channel Tunnel.
It is not know have far into the tunnel they had managed to get before being discovered.
Officials in France are now handling the matter.
A Eurotunnel spokesperson said: “Eurotunnel can confirm that a person was detected inside the Channel Tunnel and taken into custody by the French authorities.
“As there is now a criminal procedure in place we are unable to comment further at this time.”
The Daily Mirror quoted French sources as saying a man had been trying to walk the length of the tunnel into France.
He had been seen disappearing into the tunnel at Folkestone in Kent, the report said.
Police on both sides of the tunnel were alerted and French officials eventually found him.
The man was arrested on 21 December, according to the Mirror report, and appeared in a French court last Wednesday.
He was remanded in custody and will appear at court again in February.
The tunnel carries Eurostar passenger trains and the Eurotunnel Shuttle for vehicles.
Trains travel at speeds of up to 100mph in the tunnel.