A stretch of rail line used by Eurostar (search) trains heading to Britain was closed off Thursday after the discovery of a suspicious package, France's train operator said.
Police received a threat by telephone, and a subsequent search turned up a suspicious package near a high-speed line north of Paris, said France's rail network, the SNCF (search). Police have called in bomb disposal experts.
Eurostar train services between Paris and London were delayed because of the alert, but no trains have been canceled, the company said Thursday. The affected line is also used by other high-speed trains heading to northern France and Belgium.
The affected rail line section is in the suburban Val d'Oise (search) region. The SNCF said authorities were trying to find alternate routes.
In the past weeks, French authorities have received terror threats from a previously unknown group calling itself AZF. The group claims to have planted nine bombs along the country's rail network and has threatened to explode them unless it is paid millions of dollars.
Information from AZF led to the recovery Feb. 21 of an explosive device buried in the bed of a railway line near Limoges in central France.
Security was increased around France after the bombings in Madrid a week ago that killed some 200 people. Some 2,500 police are patrolling Paris' train stations along with 600 soldiers under the stepped-up measures that have also increased security at airports and other sensitive public sites.
In London, police said the French security alert and delay was unrelated to Thursday's arrest of a man walking near the English portal of the Channel Tunnel.
The man was arrested and being questioned under Britain's Terrorism Act, police said, and a security check was being carried out on the track near the port town of Dover in southeastern England.