SAN DIEGO -- Authorities warned the public Thursday to beware of a type of telephone scam that has swindled several San Diego-area senior citizens out of thousands or tens of thousands of dollars each.

The perpetrators of the crimes call older people, claiming to be a grandchild or a law enforcement officer, and ask them to wire funds to help out with some type of legal problem the supposed relative has gotten into in Canada, according to police.

"The caller usually requests the money to be transferred via a company that provides electronic funds transfer and tells the victim that he will call back to get the transaction reference number," SDPD spokeswoman Monica Munoz said. "If the scammer gets his money, he calls back asking for more money."

To keep the scheme under wraps for as long as possible, the swindlers, pretending to be embarrassed about their purported monetary problems, convince the victims to "be discreet" about the request for financial help, Munoz said.

The local victims have lost amounts ranging from $2,000 to $85,000, according to police.

Investigators do not know how the crooks decide whom to target, according to Munoz.

"They may be using Internet search engines to dig up information on individuals," she said.

Police believe the perpetrators of the scam operate out of Canada, where more than 1,000 people -- mostly senior citizens -- were victimized by mass-marketing fraud rings in one recent year, Munoz said.