Four people have been charged in a scheme that used telemarketing tactics to shake down immigrants for ransom money under the guise that loved ones had been kidnapped.

In reality, no one had been snatched and the callers didn't even know who they were dialing. An indictment against four people accused of picking up ransom payments in the San Diego area and bringing the money to Tijuana was unsealed Friday.

According to investigators, few people took the bait in the scheme in which phone numbers were chosen at random, but it still brought in at least $500,000 for its occasional successes since 2007.

Investigators say the scheme used scripts and other tactics more common in telemarketing.

Callers in Tijuana, Mexico, used about 30 different phone numbers to make up to 5,000 calls a day.