Passengers at London Bridge railway station are experiencing delays of more than an hour due to a broken-down freight train.
The disruption, expected to last until 17:00 GMT, comes after thousands of people were stranded last week during rush hour and police had to be called.
Southern services are currently affected and Thameslink trains are unable to use the station.
Passengers reported being stuck on trains outside the station.
One traveller, Ket Thiru, tweeted: “Cheers Southern. Currently one hour and counting into London Bridge.
“Everyone calm at the moment but you wait until our phone batteries expire.”
Another said hundreds of thousands of rail passengers into London Bridge were delayed.
The latest delays add to disruption caused by long-running engineering works.