A tube line running across London's congestion charging area that was closed after a derailment last month might not reopen until April, London Underground said yesterday.
The company refused to give a date for Central Line services to resume, but admitted that passengers would have to wait weeks.
Managers conceded that after an investigation lasting nearly a month they had failed to find the cause of the derailment. While they had established that an undercarriage motor broke loose, they are still not sure why, according to an interim report into the accident on 25 January in which 32 were hurt.
To remove all 750 passengers from the stricken train after it derailed at Chancery Lane took one hour. Emergency lighting lasted less than half an hour.
More than 80 similar trains were taken out of service on the Central and Waterloo & City lines so that their motors could be examined. The Waterloo & City Line restarted on Tuesday, but within hours some trains were taken out of service so that bolts holding motors could be tightened.
The Central Line will not be operational until "March or April", a spokeswoman said. "We don't want to give a specific date, because quite rightly we would be held to it."
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