MORGANTOWN, W.Va. -- Late this spring, Mylan Inc. took the unusual step of halting production at its sprawling generic drug manufacturing plant in Morgantown for an emergency meeting. Hundreds of employees, gathered in the cafeteria, were about to hear a bombshell.

Days earlier, Mylan learned two production workers had violated government-mandated quality control procedures intended to ensure the safety and effectiveness of prescription drugs. The company was launching a probe.

Publicly, Mylan officials have refused to discuss or even acknowledge the matter.

But according to a confidential internal report obtained by the Pittsburgh Post-Gazette, the company discovered that workers were routinely overriding computer-generated warnings about potential problems with the medications they were producing.

The violations of standard operating procedure at the world's third largest generic drug company, uncovered May 11, were "very serious," the report stated, involving "falsifying information" and "altering product."

The report said the practice was "pervasive," occurring on all three shifts at the plant, which makes roughly 19 billion doses of medication annually. The drugs are used to treat diabetes, high blood pressure, depression, cancer, epilepsy and other conditions.

The report did not say how long the unauthorized practice had been going on at the plant, which employs about 2,000. One worker interviewed by company investigators indicated it had been happening for at least two years.

Former Food and Drug Administration inspectors and industry consultants say the widespread breach of protocol raises troubling questions about the integrity and oversight of the plant's quality control operations.

"I've never before seen anything like this, that has reached this level of cheating," said James Akers, a longtime pharmaceutical industry consultant in Kansas City, Mo., who reviewed the document for the newspaper. "It certainly indicates a significant problem within their company."

Mylan's report offered conflicting and sometimes changing versions of what happened. When questioned by company investigators, most workers said they did not remember who showed them how to get around alerts designed to ensure drugs are properly made.

Although supervisors told the company they were unaware of what production workers were doing, some workers said supervisors were aware of the practice. At least one worker said supervisors directed her to break protocol.

Roughly a week after the breach was discovered, Mylan's quality assurance team had concluded that no medications were compromised, the report said. It did not say how the company made that determination.

In response to the breach, the report said, two union workers were suspended for 15 days and Mylan's quality team was to provide additional training and "evaluate the possibility" of revisions to the computerized quality control data management system used on the production line.

Company officials did not respond to requests for interviews for this story and did not respond to a series of questions faxed and e-mailed to Mylan's corporate offices in Cecil.

Last month, when Mylan officials learned that the newspaper had contacted several employees about the matter, CEO Robert Coury issued a memo reminding employees of the company's policy prohibiting unauthorized employees from talking with the news media.