Although investigators have declared that Justice Antonin Scalia had died of natural causes and that there was no foul play involved, mystery continues to shroud his death amid the unusual circumstances before and during the discovery of his body.

The highly respected 79-year-old U.S. Supreme Court associate justice was found dead in his resort hotel room at Cibolo Creek Ranch in Texas on Saturday, WND reported.

According to Houston businessman and ranch owner John Poindexter, Scalia was "animated and engaged" during dinner Friday night. He was one of Poindexter's 36 guests that day.

Speaking to the San Antonio Express-News, Poindexter said, "Scalia was seated near me and I had a chance to observe him. He was very entertaining. But about 9 p.m. he said, 'It's been a long day and a long week, I want to get some sleep.'"

Poindexter said he knocked on Scalia's door at about 8:30 the next morning. The door was locked and the judge did not answer. Three hours later, the ranch owner returned from an outing and found Scalia still had not come out of his room.

Poindexter then went to Scalia's room again, unlocked the door and "discovered the judge in bed, a pillow over his head. His bed clothes were unwrinkled."

"He was lying very restfully. It looked like he had not quite awakened from a nap," he said.

"His hands were sort of almost folded on top of the sheets," Poindexter told the New York Times. "The sheets weren't rumpled up at all."

He said Scalia did not have a pulse and his body was cold. After consulting with a doctor at a hospital in Alpine, Poindexter realised that resuscitation would be pointless.

Authorities in remote West Texas then contacted Presidio County Judge Cinderela Guevara who pronounced Scalia dead of natural causes even without seeing the body. She also decided not to order an autopsy.

A second justice of the peace, who was called but couldn't get to Scalia's body in time, said she would have ordered an autopsy, according to WND.

However, Scalia's family reportedly refused to have the justice's body autopsied.

Guevara admitted that she pronounced Scalia dead by phone, without seeing his body, and just relied on the statements made by law enforcement officials at the scene who assured her "there were no signs of foul play."

She said she also talked to Scalia's physician in Washington, who said that the justice suffered from a host of chronic conditions.

However, Guevara denied a report by a Dallas TV station that quoted her as saying that Scalia had died of "myocardial infarction." In an interview with The Washington Post, she said she meant only that his heart had stopped.

"It wasn't a heart attack," Guevara said. "He died of natural causes."

But despite Guevara's clarification that Scalia did not die of myocardial infarction, WFAA-TV in Dallas said the death certificate would show the cause of the death was a heart attack.