STROOD rail tunnel has again been closed because of chalkfall. The railway tunnel was shut down at 7.10am today following a minor fall and passengers were transferred to buses going between Strood and Gravesend.

The tunnel remained closed as we went to press and a Network Rail spokesman said: “Our engineers are at the site and the tunnel will remain closed until their examination is complete.’’

The alarm had first been raised when the driver of the 05.38 Charing Cross to Strood serviced noticed an area of fallen chalk.

The tunnel has had a long history of chalkfalls and was due to close in January for an entire year for permanent repairs.

The work, estimated at tens of millions of pounds, also covers the neighbouring Higham Tunnel and Network Rail believes it is the biggest tunnel rebuild in rail history.

The NR spokesman said: “This latest incident demonstrates the importance of this project.’’

Chalkfalls at the tunnel go back as far as the 1960s, with two particularly serious ones in 1967 and 1971. A heavy fall derailed a train in 1999 and 20mph speed limit has been in force in the tunnel since.

In June 2000 a shaft collapsed, causing a hole the size of a football pitch centre circle and 100ft deep.

The chalkfalls are believed to be caused by vibrations from trains or water flow because chalk is porous.