A couple who underwent Botox injections (search) last week were hospitalized with botulism poisoning, and health officials were attempting to determine whether the injections were to blame.

The man and woman, both in their 50s, were in critical condition Sunday at Palm Beach Gardens Medical Center and were breathing through ventilators, said Dr. Charles Schallop, a neurologist treating them. Hospital officials did not immediately return a call Monday to update their condition.

In New Jersey, Department of Health spokeswoman Gretchen Michael said health officials are monitoring two other patients there who might have botulism. Officials are working with the Florida Department of Health, although no link between the cases has been confirmed, Michael said.

Botulism is a rare and potentially fatal paralytic illness that affects muscles, eyes, limbs and respiratory tract. Botox is a derivative of the botulism toxin (search) that is used as a muscle relaxant and an anti-wrinkle drug.

But officials at Allergan Inc., the company that makes Botox, stress Botox's safety record, dating to the late 1970s, when clinical trials of the drug began. Just seven people in the 1990s had serious side effects, according to Allergan.

Bonnie Hebert, a spokeswoman for the federal Centers for Disease Control and Prevention, said the agency is investigating the cause of the illnesses in the two states, along with the Food and Drug Administration and the state health departments.

Schallop said the couple in Florida told him they went to the Advanced Integrated Medical Center last Wednesday to receive Botox injections, and that the couple now in New Jersey also was at the Florida clinic. He said he suspects both couples might have received the illness from either contaminated doses of Botox or some other drug.

Stephanie Fagan, a spokeswoman for Allergan, said her company found out about the illnesses on Sunday and was working with authorities to determine whether its products were sent to Advanced Integrated Medical Center.

"We're treating the matter seriously and trying to get all the details," Fagan said.

Botox use in fighting wrinkles has become so casual that people have been injected at spas and even parties. But some patients have suffered serious, and even fatal, reactions. A 43-year-old woman in Gainesville died last year after having an allergic reaction to Botox, according to autopsy results. The woman went into cardiac arrest and could not be revived.

Botox has also been cited for use against migraines, muscle spasms and abnormal sweating.