Some FM radio services in parts of the east of England have been affected after a transmitter caught fire.
The mast collapsed onto its side after the fire
The 580ft mast at Morborne, Peterborough, Cambs, caught fire on Saturday, collapsing onto transmitter buildings and neighbouring fields.
Radios 1,2, 3 and 4, BBC Radio Cambridgeshire, BBC digital radio and Classic FM were all affected, along with some mobile telephone reception.
Detectives think the fire may have been deliberate and appealed for witnesses.
Gary Martin of Cambs Police, said: "We have a number of theories and we're not resting on any particular one.
"But we need to know - was there anyone suspicious in the area or were there any bangs or fireworks or rockets flying through the air?
FM reception in parts of several counties has been affected
"Has anyone seen where the tower was ablaze - was it at the top of the tower, the middle or the bottom of the tower?"
Following the fire, an estimated 1.3m radio listeners were without an FM service.
Broadcasters are working to restore service and it is unclear how many areas are still affected.
The transmitter, which is owned by Crown Castle International, covers Cambs, and parts of Lincs, Northants, Leicestershire, Beds, Bucks and west Norfolk.