A gas explosion which destroyed a terraced house, killing a 79-year-old grandmother, was likely caused by an accidental gas leak in the home’s pipework, an investigation has found.

The cause of the fatal blast in Dulwich Road, Birmingham, on Sunday night, was determined as an “accidental and inadvertent ignition of a large escape of gas from a joint in the pipework”, police, fire and Health and Safety Executive (HSE) officials said in a statement on Thursday.

The woman who died is understood to be Doreen Rees-Bibb, although formal identification has still to be completed.

A critically injured man was dug out of the burning rubble of the home by about a dozen members of the public, whose heroic and quick-thinking actions were praised by the emergency services.

He remained in a critical but stable condition in the Queen Elizabeth Hospital Birmingham on Thursday.

In a statement, the HSE, West Midlands Fire Service and West Midlands Police said demolition work had allowed investigators “to safely access and test sections of the property’s internal gas piping”.

The HSE is continuing investigations as to whether any work-related activities contributed towards the incident.