Baxter International Inc. (BAX) said Thursday that it had received a subpoena last month seeking documents regarding its long-troubled Colleague fluid infusion pumps.

The subpoena came from the U.S. Attorney of the Northern District of Illinois, Baxter said in a 10-Q filing with the Securities and Exchange Commission. The company said it is fully cooperating with the request.

Baxter also disclosed in the filing that it now faces, along with other companies, nine lawsuits filed in various U.S. federal courts alleging that Baxter and certain competitors "conspired to restrict output and artificially increase the price of plasma-derived therapies since 2004."

Baxter disclosed three months ago that one hospital customer had filed a lawsuit on the matter. Industry dynamics in the plasma market came into focus earlier this year when the U.S. Federal Trade Commission blocked CSL Ltd. (CSL.AU) from acquiring Talecris Biotherapeutics Holdings Corp. (TLCR) for $3.1 billion amid concerns the industry "already operates as a tight oligopoly."

The Colleague pumps are a long-running trouble spot for the Deerfield, Ill., company. They were first pulled from the market in 2005 amid a host of problems and defects linked to some deaths, and Baxter has found other issues with the pumps since then, including software glitches identified in a January letter to customers.

Baxter shares were recently down 30 cents to $53.99 in after-hours trading after slipping 24 cents during Thursday's regular trading hours.

-By Jon Kamp, Dow Jones Newswires; 617-654-6728; jon.kamp@dowjones.com