East Midlands Trains said Nottingham Station had been evacuated and the fire services are on site working to contain the fire to re-open the station.
Supt Sandra England of British Transport Police, said: "We have reason to believe the fire may have been started deliberately".
Police are investigating the cause of a huge fire at Nottingham railway station, which was tackled by 60 firefighters at its height.
He said crews were still inside and trying to contain the fire between the new part of the station and the main building, describing the operation as "difficult and protracted".
The fire engulfed the station this morning and spread to the roof leading to significant delays on the rail network.
Station manager at Notts Fire and Rescue Craig Day Tweeted to say: "I would like to say a massive thank you to Nottingham #rapidreliefteam that have been supporting the emergency services and all the agencies working hard at #NottinghamTrainStation".
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Overcrowding and cancellations wrought by the third rail strike in a week were compounded last night by a warning that passengers seeking compensation would find the rules "surprisingly complicated".
The Grade II listed station was built in the mid-19th century and refurbished in recent years.
"We expect the station to remain closed and East Midlands Trains services to and from Nottingham to be disrupted throughout the rest of today, Friday 12 January". She said there were no reported casualties.
Dr Remigius Ilione, 49, said: "I drove into the vehicle park and I could already hear the fire alarm".
Several roads surrounding the station have also been closed, so traffic may be heavier than usual in the city.
EMT also Tweeted to say: "We're working with emergency services to open access to the station vehicle park at Nottingham; unfortunately it isn't safe to access at the moment so remains closed". This means we have no service from the Forest to Clifton South or Toton Lane. East Midlands Trains has done a great job ensuring no-one was hurt and everyone was evacuated safely.