A woman preparing food at a bakery was threatened by masked men, one wielding a hammer, during a hold-up early today.
Three men smashed into the Mapua Village Bakery about 30km from Nelson at 3.30am.
Detective Senior Sergeant Craig Johnston said one man was armed with a hammer and another threatened to hurt the woman if she didn't hand over cash.
All three robbers had their faces covered.
Two shop tills containing an unknown amount of loose cash were stolen.
Johnston said the baker was shaken but uninjured.
He said it was not believed to be linked to an attempted robbery at a Main Rd store in Lower Moutere on Monday.
Police were keen to hear from anyone who had information about the robbery or knew who the robbers were.
They also wanted to hear from anyone who might have witnessed any other suspicious activity around the Mapua area recently.
Anyone with information should call Nelson police on (03) 546 3840 or anonymously on 0800 555 111.