Thousands of London commuters will receive new Oyster cards today after a glitch wiped as many as 40,000 cards.

A software error meant that cards used on Saturday between 5.30am and 10.30am were deactivated by Transport for London's (TFL) card readers. Machines used to put money on the cards were also affected.

"All passengers who incur a maximum fare on Saturday 12 July will be given an automatic refund from Tuesday. They do not need to take any action," said TFL.

"We are investigating the cause of the problem, and will ensure that any necessary refunds are honoured. We apologise to our passengers for any inconvenience caused."

Once the error was discovered turnstiles were left open to stop anyone else having their cards wiped. TFL has now taken on 150 temporary staff to handle the replacement of cards.

An investigation has now been launched to find the precise cause of the problem.