POLICE believe that two of the men killed in the Hull building tragedy at the beginning of April were starting their first day of work at the site.
It is now thought roofers Tony Laughton, 38, and Shaughan Walsh, 43, had just started work when the internal floors of the building on Cleveland Street caved in. A third man, welder Dave Jowett, 44, was also killed in the tragedy earlier this month.
Det Chief Insp Bill Sparnon, who is leading the investigation, said: 'One of the issues we're exploring is that it was the two roofers' first day on the job.'
The building, a former warehouse which was being converted into a bed- and-breakfast development, has since been demolished and police have removed a number of samples for structural analysis.
Det Chief Insp Sparnon said the police inquiry was also focusing on the structural history of the building, which is thought to date back to the 1850s.
Humberside Police are jointly investigating the case with the Health and Safety Executive.
Police had originally thought there were no contractors working on the site.
Detectives are still appealing for anyone who had worked on the building in recent years to come forward.