London Underground was restoring all tube services on Wednesday after a planned three-day strike by maintenance workers was suspended after 30 hours.
But it was unable to say when the network would be fully restored and three lines were still out of action towards mid-day.
About 2,300 staff at collapsed contractor Metronet walked out at 6 p.m. on Monday in a row over jobs and pensions, bringing all but two lines to a halt and causing chaos for millions of commuters.
Transport for London (TfL), which runs the Tube network, said it welcomed the suspension of the strike, but stressed it had offered nothing new in negotiations.
Many of the 3 million passengers who use the Tube each day were forced to find alternative routes to work on Tuesday and the city's buses were packed.
Although the strike was suspended on Tuesday night, problems remained on Wednesday morning.
The Circle, Hammersmith and City and East London lines were still suspended at 11 a.m.
A TfL spokesman said rail staff were working tirelessly to restore the entire network, which involved checking tracks, points and signalling equipment.
But he added: "I wouldn't like to speculate when a full service will be restored, other than to say that the process is taking place."
RMT union leader Bob Crow told Reuters that while the strike had been suspended, another was still planned for Monday Sept. 10 -- pending the outcome of further talks.
He said this week's strike was called off after assurances over job losses, transfers and a written commitment to withdraw the original pension-scheme rescue.
"This means that our members will now actually have their pensions restored to them, which is rather different than promises from a man in an expensive suit," said Crow.
