Cleat Hill borehole being filled with cement

Emergency services were called to Cleat Hill on Saturday, 19 October

A 100m (328ft) borehole close to the scene of a fatal explosion and house fire is being filled with cement to ensure it is "gas tight", according to safety officers.

Eighty-five year-old Paul Swales died in the blast at Cleat Hill in Bedford on 19 October. Julia Harris, 84, died in hospital of her injuries 10 days later.

The Health and Safety Executive (HSE) said a plug of 15m (49ft) had been placed in the borehole and it was "confident the cement is holding the gas back".

A British Geological Survey team, which has been on site since 21 October, said it was continuing to monitor the area for gas and said that since filling work began gas levels had been reducing.

A man and a woman died following the blast at the house

Bedfordshire Fire and Rescue Service, which has maintained a 24-hour presence at the scene, said it had "yet to determine the exact cause" of the explosion but that investigations were continuing.

The explosion occurred in the same area where, on 2 July, contractors struck a pocket of natural gas while drilling a borehole to install a heat pump, causing the evacuation of nearby properties.

A separate ongoing investigation is under way into the circumstances of the July leak.

Since the incident on 19 October, about 50 households were evacuated - and a 100m cordon around the area remains in place.

Paul Swales, aged 85, died after the explosion and fire at the house in Cleat Hill earlier this month

Paul Bradley, from the HSE, told a meeting of residents that it had been "an eventful few days".

He confirmed that mud had been placed into the hole as well as cement, at a depth of 102m (335ft).

A "plug of 15m of oil and gas cement has been placed in there, that has been set and has cured," he confirmed.

"The 15m plug in the bottom is actually gas tight, that it's holding the gas where we want it to be."

He said the plan was to keep on adding cement all the way to the surface before it is fully sealed.

"We are confident the cement is holding the gas back," he added.

A number of road and footpaths closures remain in the Cleat Hill area of Bedford

Michelle Bentham, from the British Geological Survey said the team had continually monitored and measured soil and atmosphere gas - and high levels of gas had been found in different locations at different times.

She confirmed there had been high levels of methane gas in the area, but since the borehole filling work those levels were reducing, a "good indication that is working".

John Finley, from the Ground Source Heat Pump Association (GSHPA), said: "This is the only occurrence of shallow gas known in over 25 years of GSHP operations in the UK."

He said it was a "tragic event" that was being taken seriously.

"Where necessary we will make changes, modify standards and procedures, already in use," he said.