OAKLAND, Calif. -- A lawsuit filed by a small Bay Area lab alleges that seven companies including medical testing giant Quest Diagnostics have overcharged the state by more than 500 percent for some procedures – an overbilling that has cost California hundreds of millions dollars.

State Attorney General Jerry Brown was scheduled to reveal the details of the civil lawsuit at a Friday press conference. While admitting the state had launched its investigation three years ago into the alleged overbilling, he had not yet named the whistle-blower that brought the practice to the state’s attention.

KTVU obtained an exclusive copy of the sealed suit on Friday that reveals the name of whistle-blower as Chris Riedel of Hunter Laboratories LLC of Campbell.

“He (Reidel) called the State of California and said I’m aware of this practice called a ‘Pull Through’ where hospitals and doctors enter into agreement with large lab companies,” Riedel’s attorney Neill McCarthy told KTVU. “What the lab companies do is say look you have 100 patients. Ten percent of those are private pay and a blood test costs us $5.”

“We are going to charge you $1 for those patients and we’ll lose money. On the other 90 percent who are Medi-Cal we are going to charge you $10. So hospitals like it because they keep their overhead down. The lab companies like it because they are making a tremendous amount of money by overcharging the state.”

According to state law, Hunter Labs will be rewarded with a share of whatever fraudulent receipts the state can recover from the seven labs. The suit alleges that the state Medi-Cal program has been overcharged by the seven labs by as much as $500 million over the last 15 years.

"Our lawyer said that if I offered to settle this case for $100 million that the other side would jump at it," Brown said in an interview with The Los Angeles Times. "These companies have funds. They're not all household names but they have money."

Among the alleged incidents of overbilling listed in the suit were a Quest lab blood test that cost $1.43 while the company charged Medi-Cal $8.59 – a 5011 percent overcharge – and a metabolic panel procedure that costs $1.90 but the state was charged $11.69.

Meanwhile another defendant in the suit – Labcorp – allegedly charged the state $23.24 for a PSA prostrate test while the actual cost was $5.52.

The suit contains a litany list of other overbillings. The companies charged in the suit had not yet responded to the claims.