Detectives are trawling through dozens of home videos of the events leading up to the devastating Eastbourne Pier fire.
The blaze, which destroyed much of the Victorian structure on Wednesday, was originally described as non-suspicious.
However police issued an appeal for witnesses on Friday after they received information to suggest the fire was started by someone either deliberately or accidently.
In the following days they received around 40 home videos and photos of the pier in the hours and minutes leading up to the fire.
Detective Inspector Mark O’Brien said he was “very pleased” with the response but called on more footage to be sent in.
He said: “We have had around 40 responses to our dedicated email address in the first couple of days with a good selection of videos and photos.
“We’re happy to receive more as someone out there might just have the picture that will give us a significant lead in this investigation."
He added that a dedicated team was working their way through all the responses, along with studying local CCTV.
Forensic information is also starting to filter back from the scenes of crime officers and fire investigators.
The blaze started in the 144-year-old Grade II-listed structure’s amusement arcade at around 3.15pm last Wednesday.
More than 80 firefighters and lifeboat volunteers battled to control the blaze which threatened to spread along the length of the pier.
It was eventually brought under control shortly before 8pm on Wednesday with the arcade reduced to a charred ruin.
Members of the public are being warned to stay away from the area under the pier.
Det Insp O’Brien described why the blaze was now being treated as suspicious.
He said: “As a result of our investigation we have received information to suggest that the fire may have been started by someone, either deliberately or accidently, and our investigation is now focusing on that.”
Anyone with information or who saw something, no matter how small, that was suspicious should email email@example.com or call 101 quoting Operation Barsham.