Residents said they were woken to what sounded like 'a bomb going off' outside their homes.
Police said the noise was loud enough for neighbours to leave their homes and see what it was.
Officers are now appealing for anyone with any information to come forward.
Police Constable Luke Bayliss, who is leading the investigation for Nottinghamshire Police, said: "We had several calls on Monday, April 26 at around 9.30pm.
"Following house to house enquiries in the Pinfold Gardens, High Ridge and Sienna Gardens area of Forest Town an amount of shrapnel was recovered.
"We are now investigating this unknown explosion.
"Thankfully we've had no reports of any injuries or any property being damaged.
"No one has seen anything, so we're asking anyone who saw anything or anyone suspicious in the area at that time to come forward as we don't know what caused the noise.
"If you can help with our enquiries please call 101, quoting incident 168 of 28 April 2021."
