Two men were arrested after police responded to a call reporting an ongoing burglary at Peterborough Museum and Art Gallery in Priestgate.
The call was made at 10:16pm and two male suspects were stopped and subsequently arrested.
They are currently in custody at Thorpe Wood Police Station.
A spokesman for Vivacity which runs the museum said: "Peterborough Police attended Peterborough Museum overnight in response to a break-in alert. We're able to confirm that none of the collections or objects housed in the building were compromised and remain safe.
"A window was smashed but all of our security systems responded as they were intended to do. The Museum is open today as normal."