(Adds comment from Mayne Pharma, background)

SYDNEY, Dec 16 (Reuters) - Shares in Australian pharmaceutical company Mayne Pharma Group Ltd fell more than 16 percent on Friday after 20 U.S states filed a lawsuit against it alleging it engaged in a conspiracy with others to fix prices on two generic drugs.

The suit was filed on Thursday against Mayne Pharma, Mylan NV, Teva Pharmaceuticals, Heritage Pharmaceuticals Inc, Aurobindo Pharma and Citron Pharma LLC.

The states allege company executives propped up the prices of the two drugs, the New York attorney general's office said in the statement.

Mayne Pharma - which has a market capitalisation of A$2.14 billion ($1.58 billion) - confirmed it had received a subpoena from the Antitrust Division of the U.S. Department of Justice.

"The board continues to believe the investigation and the legal proceedings will not have a material impact on its future earnings," the company said in a statement to the Australian Stock Exchange.

The civil lawsuit is one piece of a broader generic drug pricing probe under way in the United States. It has grown over the past two years to include multiple drugs and companies.

($1 = 1.3585 Australian dollars) (Reporting by Colin Packham; Editing by Stephen Coates)