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
Kirkleatham Museum visitors will be able to gaze at a range of miniature marvels as a major Lego exhibition comes to the borough.
Young mum Faye Keeler is facing parenthood alone after her 'perfect' partner Chris Earl was killed in a motorbike accident near their home.
100s gathered at a Hartlepool school to release balloons in memory of the two children who were killed in a horrific French car crash.