The Oyster system used on London's transport network has broken down, two weeks after another fault left 40,000 customers with corrupted cards.
The Oyster system used on London's transport system broke down during morning rush hour, two weeks after a similar fault corrupted 40,000 cards.
The latest technical problem has affected pay-as-you-go Oystercards on the Tube network.
The latest technical problem affected pay-as-you-go Oyster cards across the Tube network from 0600 BST.
Ticket barriers are being kept open at all stations until the problem is fixed, Transport for London (TfL) said.
At one point, ticket barriers at all Tube stations were kept open as engineers tackled the problem.
Transport for London (TfL) said it had fixed the fault and Oyster readers were progressively coming back into use.
The cards are used as a form of payment across the city on the Tube, buses, trams and the Docklands Light Railway.
The cards are used as a form of payment across the city on the Tube, buses, trams and the Docklands Light Railway.
Automatic refund
Automatic refund
Passengers touch the electronic card on a reader on entry or exit to a station, or when getting on a bus.
Passengers touch the electronic card on a reader on entry or exit to a station, or when getting on a bus.
"There is currently a technical problem with Oyster readers at London Underground stations which is affecting pay-as-you-go cards only," a TfL spokesman said.
"There has been a technical problem with Oyster readers at London Underground stations this morning which has affected Oyster pay-as-you-go cards only," said a TfL spokesman.
"Ticket barriers have been opened to minimise any disruption to passengers whilst engineers work to resolve the problem."
"Oyster card readers on London Buses and on the Tram network have been unaffected."
An automatic refund would be given to any passengers charged the maximum £4 fare as a result of not being able to touch in and out at the beginning and end of their journeys, a TfL spokesman said.
An automatic refund would be given to any passengers charged the maximum £4 fare as a result of not being able to touch in and out at the beginning and end of their journeys, a TfL spokesman said.
He also said cards were not being corrupted as a result of the problem.
He also said cards were not being corrupted as a result of the problem.
About 17 million cards have been issued since the introduction of the Oyster system in 2003, TfL said.
About 17 million cards have been issued since the introduction of the Oyster system in 2003, TfL said.
Have you experienced problems with your Oyster card? Send us your comments by completing the form below.
/>Have you experienced problems with your Oyster card? Send us your comments by completing the form below.
