A Transport for London spokesperson said:
The Central line is currently suspended between Woodford / Newbury Park and Liverpool Street in both directions due to a train being taken out of service at Leyton after the driver reported smelling smoke. This has been investigated and all passengers left the train and station without reported problems.
Our staff on the ground are advising Olympic spectators to use a range of other services to reach the venues at Stratford, including Hammersmith & City line services, which interchange with the DLR, and Greater Anglia rail services. Stratford is also accessible via Javellin, Jubilee line and London Overground. London Underground tickets are being accepted on local bus services and Greater Anglia.