As many as 75 scientists working in government laboratories may have been exposed to live anthrax bacteria, the Centers for Disease Control and Prevention said on Thursday. The scientists are being offered treatment to prevent infection.

"Out of an abundance of caution, CDC is taking aggressive steps to protect the health of all involved, including protective courses of antibiotics for potentially exposed staff," spokesman Tom Skinner said in a statement. "Based on most of the potential exposure scenarios, the risk of infection is very low."

The potential exposure occurred after researchers working in a high-level biosecurity laboratory at the agency's Atlanta campus failed to follow proper procedures to inactivate the bacteria. They then transferred the samples to lower-security CDC labs not equipped to handle live anthrax. Because workers believed the samples were inactivated, they were not wearing adequate protective equipment.

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- Reuters contributed to this report.