JOHN Travolta says he and his wife Kelly Preston are heartbroken over the death of their chronically ill 16-year-old son, who collapsed at the family's holiday home on Grand Bahama.

Police Superintendent Basil Rahming has said a caretaker found Jett Travolta unconscious in a bathroom late on Friday morning and he was later pronounced dead at a Freeport hospital.

The youth was last seen entering the bathroom on Thursday, according to Rahming's police statement.

"We are heartbroken that our time with him was so brief. We will cherish the time we had with him for the rest of our lives," Travolta and Preston said on Saturday in their first public statement since Jett's death.

They also thanked people for their support.

"Jett was the most wonderful son that two parents could ever ask for and lit up the lives of everyone he encountered," said a statement posted on Travolta's website on Sunday.

"We will cherish the time we had with him for the rest of our lives."

The couple have said that Jett became sick when he was two years old and was diagnosed with Kawasaki Syndrome, an illness that leads to inflamed blood vessels in young children.

Preston blamed household cleaners and fertilisers, and said that a detoxification program based on teachings from the Church of Scientology helped improve his health, according to People magazine.

Others said Jett was prone to seizures.

Michael McDermott, a lawyer for the actor, said on Sunday that while Jett was last seen on Thursday and found the following day, he doesn't believe the teen was in the bathroom for a substantial amount of time.

"The police left the impression that the boy was unsupervised. No. There were two nannies with him for the entire evening," McDermott said.

"They made it seem like he was sent to the condo and nobody checked in on him until the next morning."

"(Jett) was spectacularly supervised," said McDermott, who said he has not had the chance to talk to the two nannies himself.

McDermott said he had no knowledge of Jett's medical history but "understood he had a history of seizures".

It is unclear whether Jett was taking medication for that.

The Bahamas' health minister, Dr Hubert Minnis, has said a second, US-certified pathologist will fly in at dawn on Monday to assist with the teenager's autopsy.

"I have spoken to (Travolta) and informed him that the government is doing everything it can," Minnis said on Sunday, adding he could not disclose further specifics about the autopsy.

About a dozen security guards and Bahamian police officers patrolled on Sunday around the luxury Old Bahama Bay resort community where Travolta and Preston remained inside their home.

The white-sand beach in front of the suites was closed.

The couple also has an eight-year-old daughter, Ella Bleu.

Travolta, 54, is trying to finish funeral arrangements and hopes to fly his son's body to Florida by midweek, McDermott said.

Travolta and Preston, 46, have a house in Ocala, Florida.

The Church of Scientology, established in 1945 by science fiction writer L.Ron Hubbard, has attracted numerous celebrity followers, and among its more famed members is Travolta, who has long been one of Hollywood's biggest names.