A young Texas couple died suddenly while on vacation in Fiji after coming down with a mystery illness, their family said.

Relatives of David and Michelle Paul were shocked Monday when authorities in Fiji called them to relay news of the couple’s tragic passing.

The couple was scheduled to return stateside Tuesday.

The State Department spokesperson told ABC News it was monitoring the local investigation.

“We offer our sincerest condolences to the family on their loss. We are closely monitoring local authorities’ investigation into the cause of death,” the spokesperson said. “We stand ready to provide all appropriate consular assistance.”

'They knew something was going on in their body'

The family said that early indications point to both husband and wife contracting a debilitating virus.

“They knew something was going on in their body and were able to get to the hospital,” Tracey Calanog, Michelle’s sister-in-law, said.

It appears that Michelle Paul died first and that David Paul passed away before he was able to be transported to Australia for further treatment.

Calanog added that the remains of the couple, who leave behind two young children, cannot be returned to the United States until a cause of death is determined.

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