Passengers are facing major disruption at one of London's busiest railway stations, BBC warns.
Network Rail said all Great Western Railway (GWR) trains between Paddington and Slough had been cancelled until at least midday after overhead electric cables were damaged at Ealing last night.
Trains between Paddington and Heathrow airport are also not running.
Services are likely to be affected all day.
GWR said damage to the overhead wires had left many trains stranded on the line between Paddington and Reading. As a result, GWR, TfL Rail and Heathrow Express will not be operating a train service between London Paddington, Hayes & Harlington or Slough until repairs have been completed.
Network Rail said it was "working to recover all the stranded trains and to rectify the damage to the overhead electric wires". It said it hoped to reopen two of the four affected lines from midday, but GWR advised passengers not to attempt to travel between Paddington and Slough until at least 12h00, local time.
Network Rail issued advice on alternative routes for passengers affected, including a replacement bus service for those heading to Heathrow.
TfL Rail services are suspended until at least 14h00.