Moorgate Underground station has reopened and trains are running as normal between Moorgate and Drayton Park rail stations again after an earlier fire alert.
A fire beside the railway tracks between Moorgate and Drayton Park stations had caused disruption on the route earlier.
National Rail said disruption on the route between the stations would continue until 11.15am.
Moorgate Underground station was closed due to the fire alert.
The Northern, Circle, Hammersmith & City and Metropolitan lines were all affected.
London Fire Brigade (LFB) was called at around 9.45am and officers went to the scene to investigate reports of a fire, an LFB spokesperson said.
Meanwhile, earlier severe delays on the Victoria line due to a person ill on a train may still be causing disruption - Transport for London warned that some trains and platforms may still be busy.