SAN FRANCISCO — Authorities in the San Francisco Bay Area arrested 89 people and seized more than 100 stolen guns, several pounds of illicit drugs and four dozen stolen vehicles after a two-year undercover operation.

The officials made the announcement Thursday at the San Francisco Police Department.

San Francisco District Attorney George Gascon said the investigation was in response to a spike in auto thefts from the rental company Zipcar.

About half the suspects are being prosecuted in federal court and the rest in state court. The U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives led the investigation, which targeted street-level auto thieves and gun trafficking. Most of the arrests were made Tuesday and Wednesday.

ATF agent Jill Snyder said the operation led to the largest number of arrests in the agency's history.