"Enquiries have been ongoing today and we now have reason to believe the fire may have been started deliberately", superintendent Sandra England said. Officers are working to identify anyone who may have been involved in the incident, and we are appealing for information from members of the public.
Around 60 firefighters tackled the blaze which started at 6:30am and spread to the main concourse and the roof.
Firefighters are still at the scene dealing with the fire, which has been brought under control.
Severe disruption was caused by the fire with the station likely to remain closed for the rest of the day.
"Our officers have been on the scene at Nottingham railway station all morning supporting Nottinghamshire Fire and Rescue firefighters as they deal with the large fire".
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".
All trains were cancelled and several cordons and East Midlands Trains advised people not to travel "unless it is absolutely necessary", warning that trains would be disrupted on all routes through Nottingham for the whole of Friday, with further disruption expected on all East Midlands train.
Commuters were evacuated from the Edwardian Grade II-listed station, and which recently underwent a £60m redevelopment, after the fire broke out at 6.30am.
"Crews are now working to stop the fire from spreading, thank you for your patience whilst we work to keep you safe!"
"Even if some trains are running by tomorrow, there will be an extremely limited service with many delays, cancellations and overcrowding".
Tram services through the station area have also been suspended, and trams from Hucknall and Phoenix Park, north of the city, are terminating at Old Market Square.