The Singapore Police Force, Immigration and Checkpoints Authority (ICA) and Singapore Customs checked close to 13,000 travelers and 350 vehicles at land, air and sea checkpoints, and scanned or searched more than 14,000 pieces of luggage and carry-on bags, the agencies said in a joint news release on Oct. 5 cited by AsiaOne.

They described the operation as part of ongoing efforts to enforce Singapore's cross-border cash reporting rules and detect other illegal cross-border activities, The Straits Times reported.

A police officer examines stacks of Singapore banknotes. Photo courtesy of Singapore Customs

Each of the seven was carrying more than S$20,000, the threshold above which cash must be declared, with the amounts ranging from S$20,400 to about S$51,000.

The largest sum was found on a 40-year-old foreign woman on Sept. 23, a day after a 46-year-old foreign man tried to bring in S$31,000, according to CNA.

A 44-year-old foreign man tried to bring in about S$23,800 on Sept. 27.

Four more travelers were caught on Sept. 28 with about S$96,400 in total.

Two of the seven received warnings and three were issued composition fines, which are paid in lieu of prosecution, totaling S$13,000. The remaining two had their cash seized for further investigation.

Travelers must declare cash or bearer negotiable instruments worth more than S$20,000, or the equivalent in foreign currency, within 72 hours before entering or leaving Singapore, using the MyICA mobile app or the ICA website.

Those who fail to report such sums, or who report them inaccurately, can be fined up to S$50,000, jailed for up to three years, or both, and the cash may be confiscated.