Some 55 lambs and two ewes have been stolen from a farm in the Lisglass Road area of Co. Derry after entry was gained to a field.
It is reported that the sheep were stolen sometime between 9am on Tuesday, August 30, 2016 and 11.30am on Monday 5, September.
The Police Service of Northern Ireland (PSNI) is appealing for information following the theft.
Constable Walsh said that the PSNI is appealing to anyone who may have witnessed any suspicious activity in the area or who may have information about the incident to contact Police at Strand Road on 101 quoting reference number 447 of the 5th.
Anyone who may be offered similar animals for sale in suspicious circumstances are also asked to contact the PSNI at Strand Road quoting the same reference number.
"Or, if someone would prefer to provide information without giving their details they can contact the independent charity Crimestoppers and speak to them anonymously on 0800 555 111," he said.
Last month in Northern Ireland, two tractors and several other items were stolen from a field on the Woodside Road in Ballymena, Co. Antrim.
It was reported that sometime between 3pm on Sunday, July 31 and 7.30am on Monday, August 1, two John Deere tractors and a red coloured McCauley low loader trailer were stolen from a field on the Woodside Road close to the GAA pitches.
The PSNI has said that a large quantity of diesel was stolen from the farm also.