When workmen turned up to carry out maintenance to a gas pipe they could have been forgiven for putting a hissing sound down to a leak.
But on closer inspection they were shocked to discover the noise was actually coming from a slithering snake.
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Staff from gas company Cadent made the surprise discovery after lifting a cover on a pipe during routine maintenance work in the Europa Link area of Tinsley on Tuesday.
A spokesperson for Cadent said: "We have found things like birds' nests in pipes in the past but nothing like this!
"It is obviously not something that you usually expect to find."
He added: "In the end they decided to leave it and not disturb the snake.
"They are due to return to complete the works once it has gone.
"We have done some research and it looks like a grass snake.
"Hopefully it will find its own way out but if not then we will call in some assistance."
It is believed the reptile got in through a small hole into the pipe.
The spokesperson confirmed that none of the staff members had been bitten.
There has been a rise in snake bites across the country recently as more people are venturing into snake habitats during the hot weather.
There are four types of snake native to the UK - Grass snake, barrel grass snake, smooth snake and the adder, which is the only venomous type.