Local farmers and landowners are being urged to be vigilant following the theft of four lambs and four ewes from near Llanidloes.
Police said the animals were taken from fields in the Llidiartywaaun area around the 9 September.
"We are asking the public to remain vigilant, check and secure the gates to any land containing livestock and report any suspicious activity to the police immediately," said PC Hannah Thrower.
Anyone with information about the theft should contact PC 491 Thrower at Llanidloes Police Station by telephoning 101.
