Two boys are in a coma and their father is paralyzed after possibly being exposed to a toxic pesticide during a vacation in the U.S. Virgin Islands, according to CNN. The family is from Delaware.

The boys are 16 and 14 and are in critical condition in a Philadelphia hospital. The father, Steve Esmond, is conscious but cannot move or speak.

The boys and their mother started having seizures on March 20, six days after they arrived at a villa in St. John. Initial reports showed methyl bromide was in the air. That chemical can cause serious damage to the brain and respiratory system.

In the U.S., it is illegal to use methyl bromide indoors, and only professionals can use it at all.

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The resort was fumigated on March 18, two days before the family became sick.

"This is a highly toxic gas that really shouldn't be used in residential areas, and the consequences could be quite severe," Dr. Patricia Salber said to CBS News.

Salber added that methyl bromide is banned in some parts of the world.

Terminix, the contractor hired to eliminate pests at the resort, said in a statement: "We're committed to performing all work we undertake in a way that is safe for our employees, customers and the public."

Read CNN's and CBS News' full stories.