The FBI hid microphones throughout the San Francisco Bay Area in order to expose real estate investors accused of fraud and bid rigging, according to CBS KPIX 5.

“They [FBI agents] put microphones under rocks, they put microphones in trees, they plant microphones in equipment,” said Jeff Harp, a KPIX 5 security analyst and former FBI agent. “I mean, there’s microphones that are planted in places that people don’t think about, because that’s the intent.”

According to the KPIX 5 report, authorities hid microphones near a bus stop and inside light fixtures outside a courthouse in Oakland.

The station reports the surveillance took place between March 2010 and January 2011. The Daily Caller reports that agents also hid microphones inside a backpack placed by one of the statues inside the court house.

Targets of the Secret Operation

Agents are targeting real estate investors accused of bid rigging at foreclosure auctions in the San Mateo and Alameda counties.

A lawyer for one of the accused plans to have the recordings dismissed as evidence because they were gathered without a warrant.

“Speaking in a public place does not mean that the individual has no reasonable expectation of privacy,” wrote the attorney in a motion to Judge Phyllis Hamilton. “Private communication in a public place qualifies as a protected ‘oral communication’… and therefore may not be intercepted without judicial authorization.”

Harp seemed to echo this view.

“An agent can’t just go out and grab a recording device and plant it somewhere without authorization from a supervisor or special agent in charge.”

Michael Marr, one of the people recorded by the devices, was indicted in 2014 on charges that he and his associates tried to rig auctions throughout Oakland. He’s pleading innocent in an ongoing case.