Forty U.S. states have filed a lawsuit against 20 pharmaceutical companies that make generic drugs, accusing the companies of participating in a scheme to inflate drug prices, sometimes by as much as 1,000%.

"We have hard evidence that shows the generic drug industry perpetrated a multibillion dollar fraud on the American people," said Connecticut Attorney General William Tong. "We all wonder why our health care and specifically the prices for generic prescription drugs, are so expensive in this country — this is a big reason why."

Generic drugs are lower price alternatives to brand name drugs.

FILE - An Israeli flag flies outside a Teva Pharma FILE - An Israeli flag flies outside a Teva Pharmaceutical Industries building, in Neot Hovav, Israel, Dec. 14, 2017. FILE - An Israeli flag flies outside a Teva Pharmaceutical Industries building, in Neot Hovav, Israel, Dec. 14, 2017.

The 500-page lawsuit, filed Friday in the U.S. District Court in Connecticut, is seeking damages, civil penalties and actions by the court to restore competition to the generic drug market. The suit accuses Teva Pharmaceuticals of being the mastermind behind the scheme.

"Teva and its co-conspirators embarked on one of the most egregious and damaging price-fixing conspiracies in the history of the United States," the suit said.

Teva Pharmaceuticals, an Israeli company, has denied the allegations and says it will fight the lawsuit.

Other drug companies named in the suit include Sandoz and Pfizer.