PHILADELPHIA (AP) — Two Delaware teenagers are still in critical condition more than six weeks after a banned pesticide was sprayed at the Caribbean resort where they were staying, their family said Monday.

Sean and Ryan Esmond and their parents fell ill after an applicator working for Terminix used the pesticide methyl bromide at the resort in the U.S. Virgin Islands.

The teens are hospitalized in Philadelphia. Their father and mother, Stephen Esmond and Theresa Devine, continue to undergo therapy, said the statement, which provided the first update on the family’s medical condition in a month.

“The Esmond Family thanks the nation for its outpouring of support and concern for the family’s recovery from this unthinkable tragedy of pesticide poisoning during their family vacation,” the statement said.

The Environmental Protection Agency, Department of Justice and authorities in the Virgin Islands are investigating.

The EPA said in April that its probe had found the toxic pesticide was used at the Sirenusa Condominium Resort in St. John several times in the past, and may have improperly been used in Puerto Rico. The agency banned the chemical for residential use in 1984.

“The family is confident that those responsible will be brought to justice,” the Esmonds’ statement said.

Stephen Esmond is head of a private middle school in Wilmington, Delaware, and Devine is a dentist in the Philadelphia suburbs.

Terminix, the Memphis, Tennessee-based pest-control firm, previously said it is cooperating with investigators and conducting its own internal inquiry.

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