Commuters face rush-hour disruption on the District Line after a signal failure at Earl's Court.
Services were suspended on the eastbound Ealing Broadway and Richmond branches for at least an hour this afternoon.
Services are up and running but with severe delays in both directions.
The stretch of the line from Barking to Upminster also has long delays.
Some passengers were left stranded on trains outside stations as services ground to a halt.
A spokesman for Transport for London said all trains had now made it to platforms so passengers could disembark.
They were not able to say when services would return to normal.
A new signalling system is due to be installed on the District Line at the beginning of 2020, although a similar project on the Metropolitan Line led to weeks of delays earlier this month.
This comes after the Standard found the District was the Underground Line with the most delays due to signal faults.
It is one of London's oldest public transport lines, although new trains have been introduced in the past few years.
Local buses are accepting tickets, as well as South Western Railway and Great Western Railway.
