Two men who held up a Hamilton Burger King restaurant are believed to have cased the premises before accosting a staff member at gunpoint.
And police are worried the offenders' confidence may be growing as they avoid capture.
Two men, one armed with a sawn-off shotgun, robbed Chartwell Burger King of an undisclosed amount of cash last Wednesday.
Detective Will Loughrin, of the Hamilton CIB, said they believe the pair may strike again.
"We believe the two men involved had familiarised themselves with the layout of the premises before they struck, laying in wait for a staff member to take out the rubbish, after closing, about 11.25pm," Mr Loughrin said.
"Putting a sawn-off shotgun to the head of the worker, the offenders have marched him back into the store where they then confronted the other workers and store manager before making off with an undisclosed sum of cash."
Mr Loughrin said a police dog handler tracked the offenders from the rear of the premises, through a gap in the fence to Rossiter Pl, across Comries Rd and on to Bellmont Ave.
"We lost the trail at the corner of Lamont St and Claremont Ave which leads us to believe the pair may have had a getaway vehicle waiting," he said.
The police are particularly interested in hearing from anyone who has seen or been offered rolls of 20c and 50c coins wrapped in white and orange, and white and black, ACM-marked paper, or from anyone who found abandoned wrapping fitting that description or clear plastic bags marked "COIN BAG".
Mr Loughrin said police also want to hear from anyone who knew of people who had suddenly come into possession of more cash than they would normally be expected to have.
The offenders were both described as being Maori or Polynesian males about 168cm tall.
One was described as being of stocky build with brown eyes wearing a black woollen scarf around his face, a black beanie on his head and a black hooded sweatshirt, pants and puffy black jacket.
The second offender was also described as being of stocky build and wearing a black hooded sweatshirt and tan pants.
Mr Loughrin said any calls with information would be treated in confidence. He can be contacted via text or phone on 027 7048 589.
Alternatively, information can be left anonymously with Crimestoppers on 0800 555 111.
- Waikato Times