U.S. Supreme Court Justice Antonin Scalia, a leading conservative voice on the high court, has died at the age of 79, a government source and a family friend told CNN on Saturday.

Scalia died in his sleep during a visit to Texas.

A government official said Scalia went to bed Friday night and told friends he wasn't feeling well. Saturday morning, he didn't get up for breakfast. And the group he was with for a hunting trip left without him.

Someone at the ranch went in to check on him and found him unresponsive.

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The U.S. Marshals Service is not investigating Scalia's death, an official told CNN. They are helping to arrange for his body to be returned.

They were present because marshals sometimes help supplement security for traveling justices.

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In a statement, Chief Justice John Roberts said he and other justices were "saddened" to hear of Scalia's passing.

"He was an extraordinary individual and jurist, admired and treasured by his colleagues," Roberts said. "His passing is a great loss to the court and the country he so loyally served. We extend our deepest condolences to his wife Maureen and his family."

Deputy White House Press Secretary Eric Schultz said President Barack Obama was informed of Scalia's passing on Saturday afternoon.

"The President and First Lady extend their deepest condolences to Justice Scalia's family. We'll have additional reaction from the President later today," Schultz said.