They are appealing for anyone that may have seen any suspicious individuals or behaviour around the nursery at the time of the incident.
Flying Start Nursery in Trinity Street was broken into between 6.20pm on Monday 13 October and 6.20 am the next day.
Thieves forced open the large gate outside the nursery, smashing the window in order to get inside the premises, at which point they escaped with the cash box containing a small amount of money.
Anyone with information is asked to contact police on 101 or Crimestoppers anonymously on 0800 5511, quoting crime reference number CR/114427/14.
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