Nine victims of a suspected fraud at the Causeway Hospital in Coleraine have been identified, police have said.
The scam at the hospital is understood to have taken place earlier this month.
Two men reportedly spent two days inside the hospital offering to help staff claim back tax.
Thousands of pounds are believed to have been lost; police believe there are more victims of the fraud and have urged them to come forward.
It is believed the fraudsters obtained the personal details of the employees, including bank details.
"We currently have nine potential victims of this alleged fraud, we believe there are more potential victims out there and we need them to contact us," said Det Insp Bob Blemmings.
"We are working closely with the Causeway Hospital to identify any potential victims and identify any suspects.
"We would advise anyone who believes they are the victim of this type of fraud to report it to their local Police station by calling 101."