FRESNO, Calif. >> Fresno’s deputy police chief was among four people arrested on federal drug charges, including conspiracy to distribute oxycodone and heroin, authorities said Thursday.

Deputy Police Chief Keith Foster, 51, was arrested for conspiracy to distribute and/or possess with the intent to distribute oxycodone, heroin and marijuana, the Federal Bureau of Investigations said in a statement.

Foster and Fresno residents Rafael Guzman, Jennifer Donebedian and Randy Flowers were arrested as result of a yearlong joint investigation by the FBI and ATF that involved wiretaps and surveillance, the FBI said.

Foster, a 29-year-veteran of the Fresno Police Department, oversaw patrol operations for the department’s four police districts. He has been a deputy chief since January 2007.

Foster has been put on paid administrative leave while the Fresno police conduct an internal investigation into alleged criminal and policy violations, the Fresno Police Department said in a statement.

“This is a very sad day for the Fresno Police Department, the citizens of Fresno, the law enforcement profession, and for me personally,” Fresno Police Chief Jerry Dyer said.

An affidavit by U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives special agent Sherri L. Reynolds shows Foster told Flowers in a Dec. 23, 2014, phone call that he had “100 of those things” for Flowers.

Foster picked up a prescription for 100 oxycodone tablets at a Rite Aid pharmacy drive-thru and then drove his black BMW to Flowers’ home on West Church Avenue in a pocket of southwest Fresno just outside city limits.

Foster picked up another prescription of oxycodone pills on Jan. 27, 2015, and then drove to Flowers’ home.

Flowers has a criminal history in Fresno County that includes a 1988 conviction for possession of cocaine base for sale; a 1994 conviction for being a felon and addict in possession of a firearm; and a 2010 conviction for delivery of a schedule II controlled substance from Marion County, Oregon, the affidavit says.

Neither the FBI nor the Fresno Police Department could provide the name of a defense attorney to comment on the charges.