An explosion, in which a child narrowly escaped injury, has prompted councillors to call for an investigation into what went wrong with the electricity supply at a block of flats.

Residents of Byfield Court, Malden Way, West Barnes, described hearing a loud bang which was “like a bomb exploding” at about 3pm on Thursday, August 9.

The building was said to be vibrating from the explosion, which was caused by water dripping on to an electrical fuse box in the basement during a cleaning of stairwells with power hoses.

The incident happened weeks after residents had to be moved out by Merton Priory Homes for seven weeks after Merton Priory Homes discovered the building’s electricity supply was in need of urgent repair.

Nadia Begum, 27, said her seven-year-old son was nearly hit by a door to the basement, which was thrown open by the blast.

She said: “It was really loud and we were petrified – the bang happened and all the lights went off. My son could have been hit.

“Everyone living here just wants this sorted out. We have been through hell and back.

“I’m a private tenant so no one put me up in a hotel. I’ve had to find somewhere to live in Pollards Hill for the last few weeks.”

After Thursday’s incident, a member of staff from the electricity provider, UK Power Networks, switched the power off and said the communal fuse box was in a dangerous condition, according to Mary-Jane Jeanes, a Merton councillor for West Barnes ward.

She said: “I am horrified that this has occurred. Residents put up with considerable stress and inconvenience for seven weeks, and their electricity supply is still not in a safe condition.”

The leader of Merton Liberal Democrats, Coun Iain Dysart, added: “Surely if proper checks had been carried out a month ago, this would have been spotted.

“This suggests that, at some stage in the recent work, someone has been negligent.”

MPH’s managing director Pauline Ford said: “We are very sorry for the impact [the] problems had on our residents at Byfield Court, which happened as a result of water from deep cleaning work leaking into the basement.

“The health and safety of our residents is our main priority, and I will be carrying out a formal investigation into what happened.

“The communal electrical supply was in urgent need of upgrading, and this work is now completed.

“All works were certified by our electrical contract and UK Power Networks were happy with the standard of work to the current legal requirements and reconnected the power to the block.

“We recognise that is has been an incredibly difficult time for our residents during the repair works, and we did everything we could to support them and complete the work as quickly as possible. The incident was totally separate to the upgrading work.”

A spokesman for UK Power Networks said: “Engineers had to isolate supplies to 18 customers in Byfield Court at around 9pm so emergency repair works could be carried out safely. All supplies were restored at 11.19pm.

“While we appreciate how frustrating it is to be without electricity, the safety of our staff and customers is our number one priority.”