KUALA LUMPUR, Malaysia (AP) — China has arrested 52 Singapore citizens in the southern region of Guangxi in a law enforcement operation targeting suspected pyramid scheme activities and related offenses, Singapore’s Foreign Ministry said Friday.

Sim Ann, Singapore’s second minister for foreign affairs, said the city-state is in contact with Chinese authorities to obtain more information on the matter. She said staff from the Singapore Embassy in Beijing have visited the 52 detainees and are providing them with consular support.

The ministry said Chinese authorities are continuing their investigations. It didn’t provide details on when the Singaporeans were arrested, their identities or the amount of money involved.

In Beijing, Chinese Foreign Ministry spokesperson Guo Jiakun told reporters Friday that China investigates and handles criminal cases involving foreign citizens in accordance with the law.

Sim said Singapore’s government doesn’t intervene in other countries’ judicial processes and investigations, but that “due process should be accorded to our citizens,” according to a transcript of her remarks on the Foreign Ministry’s website.

Sim urged Singaporeans to exercise caution when considering business or investment schemes, especially those involving the recruitment of new participants, the upfront payment of substantial sums of money or promises of unusually high returns.

Pyramid schemes typically require participants to pay to join and recruit others, with financial returns depending largely on bringing in new participants and their payments.

The Associated Press