NEW YORK (CNN/Money) - Chiron Corp., the company that made the flu vaccine that was pulled from the market last week due to safety concerns, has received a federal grand jury subpoena about problems with the drug, the company said Tuesday.

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Chiron said it intends to fully cooperate with the probe by the U.S. Attorney's Office for the Southern District of New York.

The company's Fluvirin influenza virus vaccine, which is made in England, was pulled from the market last week because of action by British health authorities. The action left the United States without nearly half the flu vaccine needed for the upcoming flu season.

Public health officials said last week that plans to vaccinate millions of people this fall would be disrupted by Chiron's Oct. 5 announcement.

And on Wall Street, the news sent investors fleeing from Chiron (CHIR: Research, Estimates) stock, which sank another 3 percent or so in before-hours trading Tuesday, Reuters reported.