The attack happened at the Post Office at the Carrington Centre on New Mill Street at around 1am on Wednesday, January 24.
Police say they believe more than one offender attacked the ATM and made off with cash before they arrived.
A spokesman for the police said: "It appears that an unknown number of offenders attacked an ATM.
"We do not currently know exactly how much money has been taken.
"The offenders left the scene before patrols arrived.
"A crime scene has been set up and crime scene investigators will be there this morning.
"There was a suggestion of the offenders possibly making off in a dark coloured vehicle.
"Enquiries are on-going."
Anyone with information is asked to contact police on 101 quoting crime reference SC1800627.