An increase in the number of reports of exploding manhole covers could be the result of faulty electrical cables damaged by the wettest winter on record.
There have been reports of 64 exploding or burning manholes so far this year, compared to 51 for the whole of 2013, according to figures released by the Health and Safety Executive and seen by the Sunday Telegraph.
In 2011 and 2012, there were nine and 31 reports respectively.
Experts believe the surge in incidents could be due to record-breaking amounts of rainfall recorded between December last year and February - the wettest winter since national records began, according to the Met Office - which could have seeped in to damaged underground power lines.
But such incidents could also be caused by other kinds of electrical faults and gas leaks.
Piccadilly Circus in central London was closed on Wednesday after multiple explosions blew off a manhole cover and set a lorry alight shortly before 11pm.
Witness Jon Hornbuckle tweeted that he saw “constant explosions every 3-4 seconds…. Low flames but huge thick black smoke.
“I was ten steps away and then BANG… Loads of fire,” he wrote.
There were no reported injuries.
Although the explosion was not directly linked to rainfall, a spokesperson for the Metropolitan Police said that the fire was “believed to have been caused by an electrical fault beneath the manhole cover.”
The cause of the incident is being investigated.
A spokesperson for the HSE told the Sunday Telegraph that the watchdog has warned UK Power Networks, which runs manholes and distributes electricity in London, to improve health and safety checks.
John Steed, the HSE’s principal specialist inspector, said: “Last year when we recorded the increase, UK Power Networks sent off failed link boxes for examination and it was concluded moisture was the predominant cause.
“We called UK Power Networks’ directors in, and we have a couple meetings with them, and we made it very clear to them that we are expecting them to manage their assets a lot better, to carry out more inspections and, as a result of that, they have actually got a couple of dedicated teams working in London, just looking at these link boxes and inspecting them."
A spokesman for UK Power Networks said:
“We believe more faults are being reported and recorded, but this does not necessarily mean there has been an increase.
“Last year one of the wettest years on record, which may also be a factor because occasionally water can seep in to cables which have been damaged by third parties.
“We regularly inspect, maintain and reinforce our network to ensure that London maintains its position as the most reliable electricity network in Britain.”