Federal regulators warned a syringe manufacturer of "several significant violations" in its quality control system two years before its needles triggered an outbreak of bacterial infections that prosecutors say led to at least five deaths and hundreds of illnesses.

A U.S. Food and Drug Administration warning letter, made public Thursday by the agency, cited AM2PAT Inc. in August 2005 for nine serious violations at its factory in Raleigh, where it made syringes of heparin and saline to flush IV lines.

The company, which was incorporated in Chicago, later moved its manufacturing to Angier, about 20 miles south of Raleigh.

Among the problems at the Raleigh factory, the letter noted poor documentation of sterility tests, insufficient efforts to maintain a sterile environment and unqualified workers. Each of those issues were cited again this month as prosecutors won guilty pleas from two former AM2PAT employees and charged former CEO Dushyant Patel.

Authorities are searching for Patel, who may have fled to his native India. Prosecutors do not know if he has an attorney. He faces up to 95 years in prison if convicted on 10 charges including fraud, false statements and selling adulterated medical devices.

The 2005 warning letter said the failure to establish and maintain procedures to control the environment "could reasonably be expected to have an adverse effect on product quality." It said the company's written quality control procedures were "obsolete" and there was no sign workers had been properly trained.

"Evidence of improperly trained personnel included an employee chewing gum while filling syringes and an employee improperly gowning during sterility testing," the warning letter stated.

Those issues apparently lingered. Prosecutors have said that the company's "microbiologist" was a teenager who had dropped out of high school. Photographs introduced as evidence show a "clean room" with a window fan patched with duct tape. Others show paint chipping off the facility's floor and syringes piled high on a table.

But the criminal case particularly focuses on how the company documented its shipments. Prosecutors contend the company was so consumed with maximizing profit that it shipped syringes without testing to ensure it they were sterile, and then later backdated paperwork to make it look as if the company had followed procedure.

AM2PAT vowed in 2005 to correct its deficiencies, according to the warning letter, and the FDA said a follow-up inspection in January 2006 was satisfactory.

On Wednesday, the FDA said the next inspection didn't take place until December 2007, and court documents show it didn't happen until after the Centers for Disease Control reported an outbreak of illness connected to AM2PAT syringes. Prosecutors say the product killed five and sickened up to 300 others, with some of the illnesses resulting in spinal meningitis and permanent brain damage.

On Thursday, the FDA said it discovered it also conducted an inspection in August 2007, after the company moved to Angier, and found only a labeling problem.

But that month, the FDA started receiving reports of dirty syringes. Some reported "orange specks" floating inside the unopened syringes, while others reported "yellow sediment" or "muddy brown" syringes filled with floating white specks.

The FDA has declined to release its inspection reports, saying they are only available through a Freedom of Information Act request, which is pending.

Plant manager Aniruddha Patel, 43, of Carpentersville, Ill., and quality control director Ravindra Kumar Sharma, 54, of Richmond, Va., each were sentenced Monday in U.S. District Court in Raleigh to 4 1/2 years in prison for fraud and allowing tainted drugs into the marketplace.