Many people in Cambridgeshire were woken by a 'loud bang' this morning.
Residents in the Ramsey area took to social media to report the noise which happened just before 8am.
It's believed that it could have been a sonic boom which happens when a plane travels faster than the speed of sound.
The Ministry of Defence told ITV News Anglia that it wasn't aware of any activity over Cambridgeshire this morning though.
Cambridgeshire Police say they're not investigating the cause of the bang.