A man was arrested early today after allegedly setting fire to luggage on a Caledonian Sleeper train.
Other passengers were moved to a different carriage on the Scotland-London train after the fire was tackled by train staff.
British Transport Police (BTP) said the alarm was raised around 3am as the train was passing Lockerbie.
It said a 21-year-old man was arrested when the train reached Carlisle.
Train staff extinguished the fire before firefighters arrived at the station and the train continued to London, arriving more than one hour late.
The carriage involved was in a section of the train from Aberdeen which had been combined with carriages from Fort William and Inverness at Waverley Station in Edinburgh en route.
A BTP spokeswoman said: "We’ve arrested a man in connection with a small fire on board a Caledonian sleeper train at around 3am this morning.
"BTP officers were informed about the fire, which is believed to have been in a luggage area, as it was travelling through Lockerbie railway station.
"Officers met the train in Carlisle and arrested a 21-year-old man on suspicion of fire-raising and theft, using cross-Border powers.
"He is being transferred back to a BTP base in Scotland to be dealt with under Scots Law.
"London-based officers met the train when it arrived at Euston railway station at around 9am in order to make further enquiries with passengers and staff."
A Caledonian Sleeper spokeswoman said: “We can confirm a small fire was set on board our Aberdeen to London Euston service this morning, where the incident was reported to Network Rail and British Transport Police.
“No guests were injured as a result of the fire, which was put out by members of staff on board the train.
Police apprehended the male passenger at Carlisle Station, where fire crews also attended to check the safety of the vehicle.
“The vehicle was taken out of passenger service to continue its journey to London.”
In 1978, 12 people died after a fire on a British Rail sleeper train at Taunton in Somerset which was caused by an electric heater.