SAN DIEGO -- An effort to halt guns, illicit drug profits and other contraband from flowing out of the United States into crime-ravaged Mexico resulted in four arrests at San Diego County's ports of entry, it was announced Thursday.

Those taken into custody Wednesday during the extensive operation were suspected of various felony and misdemeanor offenses, including narcotics possession, violation of probation and outstanding DUI warrants, sheriff's spokeswoman Jan Caldwell said.

Personnel from various law enforcement agencies also issued 43 citations and impounded 25 vehicles during interviews of about 500 pedestrians and checks of nearly 3,000 southbound autos, according to Caldwell.

No firearms were seized, she said.

San Diego County Sheriff Bill Kolender described the crackdown as a "targeted, multi-agency approach to protect our citizens and assist the Mexican government with its anti-narco-violence efforts."

"The increased drug-related violence in Mexico has been facilitated by the flow of guns and illicit funds transported from the U.S. into Mexico," Kolender said.

Taking part in the operation -- which covered the region's three land ports of entry and the ocean in the area of the international boundary -- were the Sheriff's Department, Coast Guard, Customs and Border Protection, California Highway Patrol, San Diego County Probation Department, Chula Vista Police Department, San Diego Harbor Police and U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.