Horse owners who have purchased the product should not use it. Instead, they should contact local waste-management authorities to determine how to destroy it without endangering animals, people or waterways, the Food and Drug Administration warned.

Miracle Leg Paint, marketed by Equine Miracle Corp. of Grapeland, Texas, contains a mercuric chloride blistering agent.

An old folk remedy for lameness and other horse leg ailments was to irritate the horse's skin with that or similar chemicals, on the theory that the blister would cause disease-fighting blood cells to descend on the area and help the original leg ailment, said Dr. Stephen Sundlof, FDA's veterinary medicine chief.

Only later did scientists discover mercury is toxic, and people who get mercury-containing agents over much of their skin can become seriously ill, even die, he added.

An Alabama veterinarian called the FDA on April 30 to say he had just autopsied a horse whose owner had applied Miracle Leg Paint. While there is no evidence the product played a role in the horse's death, Sundlof said, it did spark an FDA investigation.

Equine Miracle Corp. was selling an unapproved drug, Sundlof said. The company agreed to recall it Thursday.

Georgia Brown, who with her husband owns Equine Miracle, angrily asked why the FDA didn't shut her down in 1999, when she first faxed the agency the ingredient label of the then-new product and before the couple invested their life savings in it. She said veterinarians are among her customers but had never voiced safety concerns.

But the FDA said it wasn't aware Brown sold the product in 1999 - officials thought she was asking permission to sell. In February 2001, the FDA wrote Brown to say she hadn't provided enough evidence to win such approval.

AP-ES-05-31-02 1311EDT