Hundreds of federal agents fanned out Wednesday morning across Southern California to serve warrants in a coast-to-coast crackdown on healthcare fraud.

An estimated three dozen people have been served with arrest and search warrants locally, but federal officials said the crackdown extends across the country. They declined to immediately offer specifics about which locations were being targeted.

FBI spokeswoman Laura Eimiller said that more than 400 agents participated in what she described as "fraud of the Medicare system through identity theft."

Most of the arrests -- but not most of the indictments -- in the operation are taking place in Los Angeles, Eimiller said.

Officials plan to provide details at a news conference at the federal building in Westwood. Other federal jurisdictions also are expected to release details of indictments related to the operation.

-- Andrew Blankstein