A MYSTERIOUS big bang which shook a town and villages could have been a sonic boom caused by an aircraft flying too fast, it has been claimed.

People across Spalding and as far as Eye, near Peterborough (Southern England), were left reeling after the boom, which was heard and felt at about 2pm on Thursday, January 12 2006.

Today, January 13, the cause of the noise is unclear, although many suspect it was a sonic boom, caused by a jet breaking through the sound barrier. But nobody can give a definite answer to the questions.

Stuart Green, a spokesman for the Ministry of Defence, said: "There is a channel for military aircraft off the east of England, and, occasionally, pilots go through it too fast.

"RAF pilots go to a lot of trouble not to make sonic bangs, and they don't like it when aircraft from other countries go too fast."

David Galloway, assistant seismologist at the British Geological Survey, said: "We have national and regional monitors which would normally trace something like a sonic boom. But I checked for half an hour either side of the time the noise was reported and nothing came up."

Inspector Dick Holmes, of Lincolnshire police, said: "We received several telephone calls from concerned members of the public. However, we have no idea what was behind the noise."

Although the noise was thought to come from directly over Spalding, it was heard by people living in Thorney and Eye, near Peterborough, and Gedney, near Wisbech.

Liz Fowler, a receptionist at the Castle Manor Leisure Centre in Albion Street, Spalding, said: "It sounded like someone had dropped a weight or pushed a machine over. It was a very loud thud.

"We rushed upstairs to see what had happened, but of course nothing was wrong.

Everyone has been talking about it. Lots of people think it was a sonic boom."

Margaret Dark, of London Road, Spalding, said her house shook under the force. She said: "All the birds flew up in the air. I thought maybe a lorry had crashed."

But Tony Walsh, RAF Wittering spokesman, said: "I have no idea what might have caused it, but it was not us.

"It sounds like a sonic boom, but our harriers don't go fast enough. We have now launched an investigation."

And Miriam Adol, spokeswoman for the Ministry of Defence, added: "As far as I am aware, there was no military activity going on which could have been responsible."