Of the suspicious deaths, 90 cases have been reviewed so far and investigators found eight that could have been tainted.
Sixteen of the arson cases are now with the Crown Prosecution Service to consider possible charges or review.
Stephen Beattie, 49, who worked for Cleveland Police from 2002 to 2011, was arrested on suspicion of perverting the course of justice in May 2011 and remains on bail.
He was suspended from duty by Cleveland Police in February 2011 and resigned in October 2011.
He faces allegations that he potentially undermined investigations with substandard work, and claims that he lied about his qualifications when involved in arson cases.
Cleveland is now reviewing all 3,308 exhibits handled by him and has classed 480 as causing the highest level of concern.
More top news
Gary Nicholson turned from being a joiner to an artist after becoming a paraplegic following an operation to remove a tumour.
A man's been sentenced to 18 months in prison and his elderly accomplices given suspended sentences for selling counterfeit cigarettes.
Police are appealing for witnesses and information after a woman was sexually assaulted in York.