Several trams in Croydon have been taken out of service after debris on the track caused damage, Transport for London has said.
On Friday morning, a shortage of trams meant there was no service on the line between East Croydon and New Addington, Elmers End and Beckenham Junction.
The line was functioning on its other parts as of 7.40am.
The debris that caused damage to the trams’ wheels has been investigated, the BBC has reported, but engineers have not been able to find what it is.
Repair work that was due to be carried out this week have been delayed due to a strike that was held by engineers.
Unite union had accused TfL of “bad faith” in how it has engaged in talks, which led to 60 staff walking out between Sunday and Thursday.
A Transport for London spokesperson said: “We would never enter conversations in bad faith, and have been open and honest throughout the process.”
TfL said that the debris was not caused by vandalism and that around 12 of the trams are out of action.
A spokesman added: “A number of our trams have unfortunately suffered damaged wheels due to debris in a section of track, which means we are currently operating a significantly reduced service across the London Trams network.
"This impact is likely to affect services into the weekend and beyond while we repair the wheels, but our priority is to put trams safely back into service as quickly as possible."
