A Hamilton man was threatened and robbed after he used social media to solicit sex.
Police said an investigation had been launched, after a man attempted to solicit sex using social media, last Monday, August 3.
Acting Detective Sergeant Andrew Hawke said after making contact with a woman, the man met with her in the Hillcrest area of Hamilton.
Two males and a female also joined the woman, he said.
"The four offenders have then threatened the male, blackmailing him to hand over money.
"They have threatened him and his flatmate with a knife before entering their address and robbing him of this money."
Mr Hawke said due to the specific methods used by the offenders and the clear planning involved, other people may have been victimised by the group.
Police asked that anyone who had any information contact Detective Constable Scott McKenzie at the Hamilton Central Police Station on 07 858 6200.
Alternatively, information can be left anonymously with Crimestoppers on 0800 555 111.