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Four teenage boys had to be rescued by fire crews after becoming stuck 100ft underground while playing Pokemon Go.

The "embarrassed" group were searching for Pokemon when they entered an underground cave known as Box mines in Wiltshire.

One of the boys then called for help after "miraculously" finding phone signal.

The 16 and 17-year-olds had been playing the smartphone game Pokemon Go, in which people search for digital characters in real-life locations.

Damien Bence, from Dorset and Wiltshire Fire and Rescue, said the "intricate" caves have many junctions and cover an area of about 72 square miles.

He told the BBC: "The fire service doesn't have a statutory duty to enter underground systems, normally we would call on other experts such as mine rescue.

"But in this case there's lots of local experts and guides, and we used one of those. We managed to lower down water and radios so they could communicate with us.

"It's [Pokemon] beyond me. I don't quite understand it, it seems to be a bit of a phenomenon at the moment.

"They were looking for these Pokemon creatures and surprisingly they didn't find any, but it's obviously leading people into dangerous situations, such as this, and things are likely to escalate if people are going to follow the rules of this game."

Pokemon Go launched in the UK on Thursday and has become a smash hit.

But the augmented reality game has sparked safety warnings. Two gamers in San Diego plunged more than 50ft from a cliff last week.