Officers from the Environmental Health team have confirmed they responded to calls of a lizard being on the loose in Halifax.
The West Yorkshire Police force confirmed earlier in the week they had received reports of a sighting in the King Cross area on Monday morning at 11.35am.
Officers attended the area but nothing was found.
Calderdale Council also confirmed they have received the same reports from the public.
Mark Thompson, Calderdale Council’s Director of Economy and Environment, said: “Following a report of an alleged monitor lizard sighting, an Environmental Health officer visited the area to investigate.
"The officer did not see a lizard and found no evidence that could be conclusively identified as relating to the presence of a lizard.
“We will continue to monitor the situation. If people do see what they believe to be a monitor lizard, we urge them to let us know, providing as much evidence as they can.”
Nile monitors, which are common in Egypt, eat insects, birds, rodents, fish, frogs, other reptiles, eggs, and any other animal small enough for them to catch.
They are also opportunistic scavengers and will eat the carcasses of dead animals.
Their habitat can range from deserts to forests and savannas. Some monitors spend their time on the ground and others live happily in trees, but most are good climbers.
Ashley Skeldon from Kings Cross, who contacted the Halifax Courier about the sighting, said: "Everyone was saying it was a crocodile but we believe it is a Nile monitor lizard and it is about five feet long.
"Yesterday morning at 10am a massive bulldog type dog went into the park and got chased out.
"We have had the police out and the Environmental Health and they found a big dog bone.
"It's been going on for possibly two or three weeks. Normally they come out in the day because they like the heat but it has been coming out when it's quiet.
"We think it's been had as an illegal pet, been let out because it has got too big and it's now a public safety problem.
"It could attack a small child if it is attacking pet cats and dogs," she said.