A fire at a timber yard in north London has led to major disruption for rush-hour commuters, with no trains able to operate between Milton Keynes and London Euston.
The blaze broke out at a timber yard in Harrow, north-west London, overnight. More than 50 firefighters were sent to the scene.
London Fire Brigade said 12 people had been evacuated from nearby homes "as a precaution".
Dozens of residents reported flames and huge plumes of smoke at Chantry Place, Harrow, while social media users reported hearing explosions.
Disruption to rail services on the West Coast Main Line was expected to continue throughout Friday.
A Network Rail spokeswoman said the fire had damaged a trackside retaining wall.
"It will need to be dismantled, made safe and rebuilt. This is a big job expected to take all day, he said.
"The West Coast Main Line will remain shut between Euston and Milton Keynes while these repairs are made."
Trains to Headstone Lane train station have been stopped, with a cordon put in place.
Station manager Jason Jones said: "We have got a very well developed fire which is extremely visible from quite a way out.
"There are propane cylinders involved so a hazard zone has been set up as cylinders can explode when exposed to heat."
The cause of the fire is not yet known.
Virgin Trains has lifted ticket restrictions meaning passengers can use services on alternative routes or travel on Saturday.
Passengers expecting to travel on the West Coast Main Line and West London Lines are being told to check with their train operator or nationalrail.co.uk before travelling.