'Hoverboards' branded fire risk by London Fire Brigade after two burst into flames whilst charging

The aftermath of a fire caused by a charging hoverboard

Four fire engines and 20 firefighters were called to a blaze in Southwark this morning - which was caused by a charging hoverboard.

The popular gadget - which has been branded illegal by the police - is now considered a fire hazard by the London Fire Brigade (LFB).

The LFB says it has sent some of the devices off to be tested.

An earlier fire, on October 11, was caused when an electric uni-cycle also sparked up.

"As both incidents involve personal transporters that were charging at the time of the fire, we'd urge people to especially keep an eye on their devices whilst they are on charge," said Charlie Pugsley, the LFB's head of fire investigation.

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A youth poses as he rides a hoverboard, which are also known as self-balancing scooters and balance boards, on October 13, 2015 in Knutsford, England.

The service also issued a warning over Twitter for fans to be wary of their Back to the Future gadgets.

It is the latest warning about the gadgets after it was declared segways and hoverboards should only be operated on private land in the UK, according to theCrown Prosecution Service.

"Any user of such a vehicle on a public road is likely at the very least to be committing the offences of using the vehicle without insurance and using the vehicle without an excise licence," it warned.

The Department of Transport said "appropriate safety clothing should be worn at all times" whilst driving a Segway.