There are big delays on several train lines this morning after a rooftop hatch near overhead wiring became loose on a train at Town Hall station at around 5am. Repairs were completed by 9am, but flow-on delays are expected to last until midday as power to that section of the track was isolated.

The T1 Western, T2 Inner-West and Leppington, T3 Bankstown, T8 Airport, and T9 Northern lines are all affected by the delays. At least 16 services have also been cancelled and Sydney Metro is advising passengers to disembark at Epping rather than Chatswood. The ABC reports there are lines around the block for rail-replacement buses at Wynyard, Newtown and Rhodes, and the extra buses are causing traffic issues on the city side of the Harbour Bridge.

Sydney trains advises passengers listen to announcements and check boards, because platforms and stopping patterns might change at short notice.

One Twitter user says a station employee at Wynyard advised him it would be faster to walk to North Sydney than wait for a train.

Check the Transport NSW site for updates.