Able Laboratories Inc. (ABRX), a maker of generic drugs, on Monday said it has suspended manufacturing operations and recalled all of its products because of improper laboratory practices, leading to a 26 percent drop in its shares.

Last Thursday Able halted all product shipments, withdrew its financial guidance and announced the resignation of its chief executive, sending its shares down as much as 80 percent.

The company did not specify the improper lab practices it had found. "I'm not able to share anything further," said Nitin Kotak, vice president of finance.

Able makes generic versions of prescription and drugs, including versions of painkillers Tylenol (search) and Vicodin and the stimulant Ritalin (search), among others. The company had sales of about $31 million in the first quarter.

The Cranford, New Jersey-based firm said it was suspending the manufacture and distribution of all of its products until it is sure they comply with good manufacturing procedures.

It also said it would withdraw applications with U.S. regulators to sell seven new products.

It said an internal investigation continues.

The disruptions will have a "material adverse effect" on its business and results, it said.

According to a warning letter sent to the company by the U.S. Food and Drug Administrationin April 2004, the company was in violation of not reporting serious side effects linked to some of its drug.

In one case, a patient was taken to an emergency room for a possible stroke, according to a letter sent to the company by the FDA (search) at that time, posted on the FDA's Web site.

Able shares were down $1.86, or 26 percent, to $5.33 on the Nasdaq stock market.