At least two Hamilton students have been victim of a scam that makes families back in China believe their children have been kidnapped.

If you're presented with a scenario you need to act upon immediately, it's likely not a legitimate agency. - Jackie Penman, Hamilton Police Service

Someone contacted two McMaster University international students from China and said their credit cards were compromised, said police spokesperson Jackie Penman. That person also told the students not to use their cell phones or be on social media.

Then someone called the students' families in China and said the students had been kidnapped, and demanded a ransom.

When those family members tried to call the students, Penman said, the students didn't answer their phones.

In both cases, the families called Hamilton police. Officers tracked down the students, who were unharmed and hadn't been kidnapped. But police worry the scammers will strike again.

Police have spread the word to McMaster University, Mohawk College and Columbia College, as well as local school boards.

These scams have happened in Toronto too. There were three over the weekend, which prompted a large search for the students, who were aged 16 to 20.

In Hamilton, both a male and female student were targeted.

"We want to encourage students to be aware of the scam," Penman said. "If they have any concerns or questions, they can reach out to Hamilton Police Service."

Also, "we want to remind individuals that if you're presented with a scenario you need to act upon immediately, it's likely not a legitimate agency."

Anyone with information that will help track down the scammers should call Det. Const. David Tsuchida at 905-546-4861, or Crime Stoppers at 1-800-222-8477.