Repairs at a railway station damaged in a major fire one year ago are likely to cost "millions", Network Rail has said.
Ten fire crews were needed to bring the fire under control after it ripped through Nottingham railway station at about 06:30 GMT on 12 January 2018.
British Transport Police said work to recover damaged CCTV footage had revealed new information, and they remain adamant the fire was deliberate.
Network Rail could not provide an exact figure for the full cost of repairs.
A 33-year-old woman from Derby was arrested on suspicion of arson but later released under investigation.
The fire started in a set of women's toilets on the new side of the station and caused "significant damage".
Det Insp Granville Sellers, from British Transport Police, said officers had been working "tirelessly" on the investigation into the blaze.
He said they stood by their assessment it had been started deliberately.
Det Insp Sellers revealed the station's CCTV hard drive had been badly damaged and the force had spent months working with digital forensic teams to recover evidence.
"This work has now been completed and has revealed new lines of enquiry which are being pursued," he said.
He said more than 150 witness statements had been taken.
Gary Walsh, from Network Rail, said the station had fully reopened, with the exception of the lifts on platform 7 that were damaged in the fire.
Repairs are due to finish in April.
Nottingham South MP and chair of the Transport Committee, Lilian Greenwood, said it was "obviously a concern" no-one had yet been charged in connection with the "devastating fire".
She said she hoped the restored CCTV would lead to someone being held to account for what happened.