The Shrewsbury explosion was caused by gas leaking from a fractured main, a report has ruled.

The gas leaked from the main under the footpath in front of 1-5 Bridge Street and seeped into the building, according to the report. It then exploded injuring 12 people – five seriously.

• Read the full report here

On the morning of January 3 last year there were four people in the landing and bedroom areas of the flat when the explosion ripped through the site at 11.26am.

Four people in the building at 1-5 Bridge Street – Scott Godbold, Sarah Pearse, Sam Devine Turner and Annie Davies, along with Kiley McDonnell, who had been starring in a pantomime at the nearby Theatre Severn – were injured and spent time in hospital.

Scott Godbold, Annie Davies and Sam Devine-Turner

All four occupants suffered major injuries after being either thrown from the building or buried in the debris, which damaged many surrounding buildings.

A family of six near their car in the car park at the time of the explosion were caught up in the blast. Two of them suffered injuries from flying debris.

The blast destroyed one building and left the town centre partially closed.

But the year-long investigation by the Health and Safety Executive found nobody was to blame as there was no evidence of any breach of safety legislation.

The nine-page document delves into the circumstances leading up to the blast on the corner of Bridge Street and Smithfield Road.

The report said: “The investigation identified a low pressure cast iron gas main, located within the footway in front of 1-5 Bridge Street which had fractured at a point approximately 1.5 metres from the property.

“There was no mains gas supply to the property.

“A pathway was identified which would have allowed gas leaking from the main to flow into the property. A number of potential ignition sources were identified within the property.

Kiley McDonnell with Matt Healey, Kim Marsh and Tom Hudson at a Theatre Severn benefit show

“Based upon debris analysis, the building damage was consistent with a natural gas explosion.”

West Mercia Police led the initial investigation into the incident and concluded there was no evidence that any person had intentionally sought to cause the fire or explosion. The investigation was subsequently handed to the HSE.

The executive worked with West Mercia Police and the Health and Safety Laboratory.

The team included HM Inspectors of Health and Safety and specialists in metallurgy and fire and explosion.

Representatives from National Grid Gas, British Telecom, Shropshire Council and Central Networks – the local electricity supplier – also contributed.

The report said: “HSE’s investigation has concluded that in relation to the main outside 1-5 Bridge Street, National Grid Gas had correctly applied their maintenance procedures.

“No factors were identified that could have indicated that this main was particularly likely to be prone to failure.

“The main had been appropriately risk assessed, was not subject to leakage reports thus not identified for proactive replacement prior to the incident.

Scott Godbold and Sarah Pearse

“The investigation identified no breaches of health and safety legislation, therefore, giving consideration to HSE’s enforcement model and enforcement policies, enforcement action is not appropriate in relation to this incident.” In the days and weeks leading up to the explosion the report explains that none of the occupants of 1-5 Bridge Street reported smelling gas. The report said the gas main outside the building dated from the 1930s.

It did not have any service pipes connecting it to any property in or near Bridge Street, the report said.

But the main had been laid in a trench containing a number of bricks and was partly laid on a brick wall which may have given rise to stress on the pipe, the report found.

A telecom chamber, which was built about 20 years ago, was close to the main and this may have placed further stress on the main, the HSE said.

But the HSE said these below-ground factors could not have been known to National Grid Gas.

The findings come after it emerged in September last year that National Grid, in a solicitor’s letter, had made allegations about BT relating to the cause of the blast.

HSE’s analysis of National Grid Gas recorded confirmed gas operating pressures in a system feeding Bridge Street were within normal pressure parameters.

Smell levels were also within acceptable parameters prior to the explosion and no reports of the smell of gas in the area were made to the gas emergency service in the weeks before the explosion, the report said. Ground conditions, including the corrosive nature of the soil, may have contributed to the unpredicted failure of the main, the HSE said.

But the HSE has brought the case to a close concluding there is no evidence of failures by the pipeline operator or any other company or individual to warrant prosecution.

By Sam Pinnington

Timeline of the Shrewsbury explosion and its aftermath

JANUARY 3: Explosion on the corner of Bridge Street and Smithfield Road leaves 12 people injured – five seriously. They are Scott Godbold, Sarah Pearse, Annie Davies, Sam Devine-Turner and Kiley McDonnell.

JANUARY14: Families of the explosion victims hold a private meeting with the organisers of the specially set-up Bridge Street Fund to discuss support for them when they leave hospital.

JANUARY 18: Scott Godbold, who lived at the flat on the corner of Bridge Street and Smithfield Road with his girlfriend Sarah Pearse, and their friend Sam Devine-Turner, are discharged from Selly Oak hospital.

FEBRUARY 12: Shropshire traders take to the streets with placards to protest over loss of business following the explosion.

FEBRUARY 19: Parking fees are suspended until March 31 in the Bridge Street, St Austins and The Tannery car parks to help businesses still suffering in the wake of the explosion.

MARCH 16: Victims of the explosion demand answers over what caused the huge blast.

MARCH 17: The Health and Safety Executive defends how long it is taking to investigate the Shrewsbury explosion — saying it was vital that the true cause was found.

APRIL 30: A benefit show in aid of panto star Kiley McDonnell becomes one of the fastest-selling events staged at the town theatre.

SEPTEMBER 27: Speculation mounts over what could have caused the explosion. It emerges that National Grid, in a solicitor’s letter, has made allegations about BT relating to the cause of the blast.

SEPTEMBER 30: Three of the victims of the explosion, Kiley McDonnell, Scott Godbold and Sarah Pearse pursue claims against BT.

OCTOBER18: A benefit gig held in support of the former panto star Kiley McDonnell was hailed a success.

JANUARY 3, 2011: On the first anniversary of the Shrewsbury blast, Health and Safety Executive chiefs reveal their report over the explosion could be released in a matter of weeks.

JANUARY 25, 2011: The Health and Safety Executive report concludes there was “no evidence of any breach of relevant safety legislation” and it would not be taking any enforcement action.