A report released by the former chairman of Massey Energy said that the explosion at the Upper Big Branch mine in West Virginia, US, that killed 29 men in April last year was caused by natural gas, not coal dust, contradicting an independent investigation.

Bobby Inman’s report said the mine had been adequately rock dusted before the explosion and the ventilation system did not cause the blast, despite the investigation suggesting inadequate ventilation led to coal dust build up.

The 102-page report titled Massey Energy‘s Preliminary Report of Investigation of the Upper Big Branch Explosion’ was released on 3 June, two days after Massey Energy was acquired by ALPHA Natural Resources for $7bn.

Alpha agreed to assume liability stemming from legal action from the incident as part of its deal to acquire Massey, reports Reuters.

However, the company has stated that it did not commission or authorise the release of the report and was not given the opportunity to review it.

Thirteen of the 29 families of miners who were killed in the explosion have sued Massey in West Virginia state courts, while eight agreed to settlement offers.