Around 2:30 Friday morning Niagara Regional Police responded alongside the Niagara Falls Fire Department for a residential structure fire located on Ailanthus Avenue south of Dunn Street in Niagara Falls. The fire was extinguished and no physical injuries were sustained as the residence was unoccupied at the time. Damage caused by the fire is estimated to be $400,000. The cause of the fire has been deemed suspicious prompting the involvement of the Ontario Fire Marshal. Detectives assigned to the 2 District Criminal Investigative Branch have assumed carriage of the investigation. They are being supported by detectives assigned to the Forensic Services Unit. Anyone who may have witnessed suspicious activity on Ailanthus Avenue or in the surrounding area are being asked to contact detectives. In addition, area residents with CCTV capabilities are being asked to review their surveillance footage and report any relevant information.To contact the lead detective dial (905) 688-4111, option 3, extension 1007730.