CHICAGO (CBS) — The Drug Enforcement Administration has issued a warning about criminals posing as DEA special agents, as part of an international extortion scheme.

WBBM Newsradio’s Dave Berner reports the DEA said the crooks call victims – usually people who have purchased prescription drugs online, or over the phone – and identify themselves as DEA agents, or law enforcement officials from another agency.

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The impersonators inform victims purchasing drugs in that way is illegal, and tell them legal action will be taken against them, unless they pay a fine.

“No DEA agent is ever going to contact somebody telephonically, and ask them for money. It’s just not going to happen,” said Owen Putnam, a special agent for the Chicago division of the DEA.

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He said 30 to 40 people have called the DEA over the past six months to complain about the scam.

The scammers instruct victims to send them money via wire transfer, to a designated location, usually overseas.

If the people they call refuse to send money, the impersonators usually threaten to arrest them.

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Anyone receiving such a call should contact the DEA by calling 877-792-2873.