The Ministry of Defence is investigating reports of a loud bang that has been heard across a large part of England.
Warwickshire Fire and Rescue Service also said it was looking into what caused the mysterious noise heard at about 18:10 BST.
Reports have come from across the West Midlands, Warwickshire and Oxfordshire.
One Coventry resident said his house shook. "I thought somebody had thrown a brick through the window," he said.
Some of those who heard it said the sound lasted just a few seconds.
The MoD said it was looking into reports of a loud bang in Oxfordshire.
The British Geological Survey also said it was investigating the incident.
There were reports of the noise being heard in Bath, Swindon, Coventry, Rugby and Oxford.
Birmingham Airport dismissed suggestions the sound could have been caused by a sonic boom as a plane came in to land. Source