Masked raiders blew up a bank cash point in the early hours of Saturday morning (November 14).
Officers were called to Barclays in Tring High Street at 4.20am following reports of an explosion.
Witnesses say men wearing balaclavas left the scene in a black Mercedes.
Police say the thieves used gas canisters in an attempt to blow up the ATM, but it is not believed they were able to steal any of the cash.
Detective Constable Pete Spiers said: “Whilst this occurred in the early hours of the morning, the sound of the blast would have woken people and they may have seen the offenders leave the scene.
“If you did witness anything and haven’t already spoken to police then please do call.
“I am also keen to hear from anyone who saw a black Mercedes in the area in suspicious circumstances too.
“Thankfully no one was injured during the incident and at no stage were any members of the public thought to be in danger.
“However some disruption has been caused within the community and I would like to thank residents for their patience.”
Anyone with any information is asked to call non-emergency number 101, quoting ISR 98 of November 14.
Alternatively contact Crimestoppers anonymously on 0800 555 111 or using their Anonymous Online Form at www.crimestoppers-uk.org.
No personal details are taken, information cannot be traced or recorded and you will not go to court.