Local FBI agents told the San Diego Union-Tribune that at least 26 San Diego County residents were kidnapped and held for ransom in the three popular Mexican communities last year, compared to 11 in 2006.

"Some of the 26 were recovered, some were hurt and some were killed," Alex Horan of the FBI's violent-crime squad in San Diego told the newspaper.

The FBI said most of the victims have business interests or family members in Mexico but anyone visiting Mexico should be cautious. The U.S. Consulate in Tijuana issued a travel advisory last week.

Horan described the kidnapping groups are sophisticated operations. "They know who they're going after," he said. "I think they have a list."