Parents have been warned to be on the lookout for an 8ft (2.4m) boa constrictor which could pose a risk to small children.
The reptile was reported missing from an address inSkelmersdale, Lancashire, on Tuesday evening.
Heavy-bodied boa constrictors, which kill their prey by wrapping themselves around it, pose a potential risk to children and animals as they might coil around them seeking warmth.
They can also deliver a nasty bite if they feel threatened.
However, they are not venomous or normally aggressive towards humans.
Sky’s Becky Johnson, reporting from Skelmersdale, said the snake might have slithered down the toilet and be hiding in the drains.
“The neighbours didn’t even know they had an 8ft boa constrictor,” she said.
“It could come up the drain at one of the neighbour’s houses, it could also be in the attic.
“Lancashire County Council have been out searching drains, but so far there is no sign of it.”
Experts said the boa constrictor was likely to be sleeping somewhere warm.
Inspector Mark Porter, ofSkelmersdalePolice, said: “While we do not believe the snake is aggressive or would attack anybody, there is the potential for risk to small children or pets from the animal seeking warmth.
“I would urge anyone who sees the snake to get in touch so that it can be recovered safely.”
The police warning came a day after two boa constrictors were found near a children’s play area in an east London park.
Police officers removed the snakes with a litter grabber and brown bags.
:: Anyone with information about the disappearance in Bearncroft, Skelmersdale, should contact police on 101, quoting log number 1586 of July 22.