The object was spotted by primary school teacher Sarah Smith, pictured, circling above Hebden Bridge in the early hours of the morning and residents across Calderdale have since added weight to the claims.

The UFO circled the town in a slow 10-minute loop at around 3am and passed over Sowerby and Greetland. It was said to be so loud people got out of their beds to see what it was.

But with the authorities denying there were any flights over the area at that time, the object remains a mystery.

Mrs Smith, who lives in Hebden Bridge and is a teacher at Warley Road Primary School, Halifax, said: "It woke me up it was so loud but the sky was very cloudy and I couldn't really make out what all the racket was.

"It sounded like some sort of helicopter but I could only see its light and not much else.

"It was rumbling and rattling but there was no searchlight coming off it.

"It was really weird to see, especially at that time in the morning."

Other people also reported hearing the flying object. One Sowerby resident said: "It was very loud and it woke me up but it was difficult to see anything but its lights. Occasionally I could see a dark mass."

In a comment posted on the Courier website, Sozza, of King Cross, Halifax, said: "I also heard something that sounded like it was right above our house. It woke my children up and I presumed it was a police helicopter.

"But thought it odd when there was nothing in the local news."

The police and military both deny any helicopter searches in Calderdale last Wednesday.

A Ministry of Defence spokesperson, said: "There was no flying activity by us in the north of England that night. It's a mystery."

There has been a recent spate of UFO sightings across Britain, with 22 in the past month alone.

Among the sightings include soldiers seeing 13 objects above their barracks at Tern Hill, Shropshire and a police helicopter reporting a close encounter with a UFO near Cardiff.