Commuters are still facing severe delays on the Victoria line this morning, after an earlier signal failure at Brixton.
Tickets are being accepted on local buses, London Overground, Great Northern, Southeastern and South Western Railway.
Nigel Holness, London Underground’s director for network operations, said: "I apologise to customers for the disruption on the Victoria line this morning, which is being caused by a complex signal points failure at Brixton. Our engineers were on site immediately and identified the fault which we're trying to fix as quickly as possible.
"We've implemented a temporary reduced timetable which means we can give customers a regular train service while we fix the problem. I advise customers to check our Twitter feeds and the TfL website for the latest updates to help them plan their journeys."
TfL advised commuters to avoid the line if possible.
"Trains and stations are likely to be very congested and crowd control measures may be introduced at some stations during the peak," TfL said.
There are also minor delays on the London Overground between Stratford and Richmond/Clapham Junction due to faulty trains.