More than 10,000 documents and exhibits relating to the Birmingham pub bombings have been viewed, collated and assessed by the West Midlands Counter Terrorism Unit.
The bombings at the Tavern in the Town and Mulbury Bush pubs in Birmingham city centre on 21 November 1974 resulted in the deaths of 21 people and 182 more were injured.
Although attributed to the IRA, the organisation never admitted responsibility for the attacks.
Six men were charged, convicted and sentenced to life in prison for the murders, but 16 years later they were released after convictions were declared unsafe and quashed at the Court of Appeal.
The new work has been carried out by the current generation of Counter Terrorism officers to ensure they are prepared with a thorough understanding of the case if new information were to come to light.
Officers expect the work to be completed in the spring of 2014, with around 80% of the work now complete. Two leading forensic scientists have also been asked to help assess the information, to see if any new forensic lines of inquiry might exist.