Police had within hours on Friday, uncovered a ploy by four foreign workers, who lied about being robbed after they lost their work permits.

The four men, who are between 24 and 42 years old, are now being investigated for making a false police report.

This after they went to Sembawang Neighbourhood Police Centre at about 11.20am on Friday and filed a report saying that they had been robbed at knifepoint near Kallang River by six unknown Indian suspects.

They said the suspects took their mobile phones and wallets containing their work permits.

Follow-up investigations, however, revealed that the four had in fact lost their work permits and had hatched a plan to report a robbery, in order to explain to their employer on the loss.

Police said in a statement that anyone who is convicted for giving any information which he knows to be false to a public servant shall be punished with imprisonment for a term which may extend to one year, or with fine which may extend to $5000, or with both.

Commander of Ang Mo Kio Police Division, Deputy Assistant Commissioner of Police Keok Tong San said the dire consequences of making such untrue reports and wasting police resources that could otherwise have been better deployed to other more urgent cases.

Separately, a total of 11 men were arrested in Geylang for various offences during an overnight operation that ended early Saturday morning.

The operation, led by Bedok Police Division, with crack troopers from the Special Operations Command, covered back lanes of Geylang.

The suspects, age between 18 and 59 years old, were arrested for various offences such as drug offences, immigration offences, gang-related activities and peddling of contraband cigarettes.

Investigations against the suspects are ongoing.

Commander of Bedok Police Division, Deputy Assistant Commissioner of Police How Kwang Hwee, said police will continue to work closely with other enforcement agencies to clamp down on criminal activities.