A huge fire at Nottingham railway station that started in a toilet block is being treated as arson, police said.
The fire began just before rush hour at 6.30am and spread to the main concourse and the roof.
A joint investigation between British Transport Police (BTP) and Nottinghamshire Fire and Rescue was launched, and BTP said on Friday evening they are treating the fire as arson.
The Grade II listed building, which had been recently refurbished, was evacuated and there were no reported injuries.
Some 60 firefighters tackled the blaze with specialist equipment and it was brought fully under control by the afternoon.
Superintendent Sandra England, who is leading the BTP response, said: "Inquiries have been ongoing and we now have reason to believe the fire may have been started deliberately.
"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.
"Fortunately, we have not had any reports of injuries as a result of the fire.
"Cordons remain in place around the area and trains are not running. It is likely the station will remain closed for the rest of the day."
The station was evacuated just before the morning rush hour, and the blaze caused widespread travel disruption across the city's transport network.
East Midlands Trains said: "It is anticipated that Nottingham station will not re-open today and we expect trains to be disrupted on all routes through Nottingham for the whole of Friday 12th January."
New transport minister Jo Johnson said: "It has been a devastating incident here at Nottingham station but it has been an extraordinary response from the emergency services.
"We have seen an exemplary evacuation this morning, there were two to three hundred passengers at the start of the rush hour who were evacuated safely and as far as we can tell nobody has been hurt in the incident.
"It is a devastating incident that has done substantial damage.
"I'm confident we will be able to get at least the bulk of the station back up and running."
The fire is causing significant travel disruption across the region.
Trains to the airport from Nottingham, Lincoln and Leicester were cancelled on Friday morning and East Midlands Trains advised people not to travel "unless it is absolutely necessary", saying trains "cannot run to/from Nottingham".
- LONDON ST PANCRAS TO NOTTINGHAM - train company working to run trains on this route to/from East Midlands Parkway
- LEICESTER / NOTTM/ LINCOLN - limited shuttle service running between Loughborough and Leicester only
- NOTTM / GRANTHAM / SKEGNESS - limited shuttle service running between Grantham and Skegness only
- MATLOCK / NOTTINGHAM - train company hoping to run trains between Matlock and Derby only
- NOTTINGHAM / MANSFIELD / WORKSOP - no service on this route today
- LIVERPOOL / NOTTINGHAM / NORWICH - train company working to divert trains away from Nottingham between Peterborough and Chesterfield - trains will not call at Grantham, Nottingham and may also be unable to call at Langley Mill, Ilkeston and Alfreton
The fire also disrupted the journeys of many airline passengers booked on flights to or from East Midlands Airport.
Aston Villa football club have also promised to help those fans planning to travel by train to the Nottingham Forest v Aston Villa game tomorrow.
Disruption is expected on all East Midlands Trains, the train operator said. Buses and trams are also affected, police said.
Asked about potential disruptions for football fans on Saturday, Kirsty Derry, deputy managing director of East Midlands Trains, told the Press Association: "We have got people working through the clock to make sure we get a really good level of service [on Saturday].
"People should check before they travel and maybe tonight it would be wise just to think about those alternative arrangements - but we are very optimistic about the level of service we can put on tomorrow."