The leader of the RMT has called for a strike ballot over safety fears

Buses were laid on to help thousands of Northern Line commuters make their journey to work on Monday after the Camden Town crash.

The train is still in the tunnel and it could take a couple of days to remove it as well as carry out checks on the track.

Seven people were injured, and two remain in hospital after part of the train came off the track and hit the tunnel wall on Sunday.

Extra buses

More than 200 people had to be led to safety after the crash which happened less than 48 hours after a derailment near Hammersmith, in west London.

Mike Strzelecki, of London Underground, said travellers should try to avoid using the Northern Line.

He said: "We will be laying on extra bus services but obviously with congestion at street level there are only so many buses we can get on the road."

There are no trains running on the line between East Finchley and Euston and from Golders Green to Charing Cross.

Tube managers are investigating reports that the sixth car was pulled from the rest of the train because of a track fault.

Since we have had it (London Underground) transferred to us in July it looks like it has just been held together by a tape and a bit of string London Mayor Ken Livingstone

However, the closure is not expected to last as long as the 11-week shutdown of the Central Line in the wake of a derailment at Chancery Lane earlier this year.

Five of those injured in the accident were discharged from hospital after treatment for minor injuries.

Two others were kept at the Royal Free Hospital in Hampstead, one with a broken thigh and the other with a head injury.

No-one was injured in the Piccadilly Line derailment near Hammersmith station on Friday evening when it is thought a rail broke beneath a train carrying 76 passengers.

Sources at the train drivers' union Aslef say members have complained about track problems at Camden Town and Hammersmith in recent weeks.

Bob Crow, head of the Rail Maritime and Transport union (RMT), threatened to recommend a ballot of members unless contracts given to private companies this year were suspended.

Emergency legislation

Tube Lines was given responsibility for repairing and upgrading the Northern, Piccadilly and Jubilee Lines this year under the Public Private Partnership scheme.

London Mayor Ken Livingstone told BBC Radio 4's Today programme he would seek emergency legislation from the Government to suspend the maintenence contracts.

He said: "It might be that this isn't the result of the partial privatisation, it could be that we have just had 19 years of under-investment in the Underground and in many areas, since we have had it transferred to us in July it looks like it has just been held together by a tape and a bit of string.

"But all my instincts are to suspect that this (partial privatisation) may be the problem, that there are too many firms involved, too much delegation, perhaps even a repeat of the mistake that we saw on the overland trains of sub-contractors and sub-contractors sub-contracting the work out."