Federal prosecutors say more charges are likely in the case of three people charged in an alleged heath care scheme involving diluted cancer drugs and old syringes at a now-closed Mississippi clinic.

Dr. Meera Sachdeva, Brittany McCoskey and Monica Weeks are charged with offenses including conspiracy, fraud and witness tampering related to Rose Cancer Center in Summit. They have pleaded not guilty in U.S. District Court in Jackson.

Prosecutors filed a motion last week asking for the case to be declared complex, which would push back the May 2 trial date and give the parties more time to prepare. The filing said there already have been 500,000 pages of documents submitted through discovery and more is expected.

“Moreover, the United States has continued to investigate additional acts by some or all of the current defendants, as well as the acts of others not currently charged, and it is likely that additional charges will be sought in the near future,” Assistant U.S. Attorney Scott Gilbert wrote in the court filing.

Authorities say the clinic made millions of dollars while diluting drugs and billing Medicaid, Medicare and insurance companies for more chemotherapy than patients received. The clinic also used old syringes on multiple patients while billing for new ones, court records said.

Prosecutors want the judge to delay the trial until November. The government said it’s waiting for input from several oncology experts and their full reports aren’t expected to be available until at least the middle of June.

Sachdeva established the clinic in south Mississippi in 2005 and billed Medicaid and Medicare for about $15.1 million during the alleged scheme. She has been held without bond since August because authorities consider her a flight risk.

She is a naturalized U.S. citizen from India. Prosecutors said she often traveled overseas and has considerable assets, including bank accounts, in her native country, despite the seizure of about $6 million.

McCoskey and Weeks are free on bond. Prosecutors say Weeks did billing for the clinic. McCoskey was a receptionist and later the office manager, prosecutors have said.

McCoskey’s lawyer, George Lucas, and Weeks’ lawyer, Cliff Johnson, had no comment when contacted Monday. Sachdeva’s lawyer did not immediately respond to a message.

The Mississippi Health Department closed the Rose Cancer Center in July 2011 because of “unsafe infection control practices” and tested hundreds of patients for viral diseases like HIV over concerns about dirty needles after 11 patients went to hospitals with the same bacterial infection.