Posting to Twitter at 5.50pm, TfL said: "Severe delays: Acton Town to Uxbridge due to an earlier signalling problem at Acton Town.
"Minor delays: Acton Town - Heathrow Terminals."
According to Twitter user @KatyxMarie, there are also delays on other parts of the line as she claimed she waited 13 minutes for a train at Caledonian road eastbound.
Those planning to travel on the Tube should head to the Transport for London (TfL) website to check their journey.
According to TfL, tickets are being accepted on local buses.
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