A teenage boy who stowed away on a flight from California to Hawaii in the frozen, oxygen-deprived wheel well of a passenger jet was resting in hospital on Tuesday, two days after his death-defying jaunt over the Pacific, a Hawaii official said.

The teenager, whose name has not been released, is "resting comfortably" at a hospital in Hawaii, Kayla Rosenfeld, spokeswoman of the state's Department of Human Services, said in a statement.

The boy, who is from Santa Clara, California, is in the custody of the department's Child Welfare Services division, and officials were working to ensure his safe return home, she said.

He told investigators he was trying to travel to Somalia to see his mother, a law enforcement official told CNN. A local CBS-affiliate reported the boy was living with his father in Santa Clara, but his mother lives in Somalia.

He ran away from home on Sunday and traveled as a stowaway in the wheel well of a Hawaiian Airlines Boeing 767 on a flight of more than five hours from San Jose International Airport to Kahului Airport in Maui, the FBI said. He crept onto the tarmac in San Jose under cover of darkness, San Jose police said.

The teen quickly lost consciousness as temperatures in the wheel well sank as low as minus 80 degrees Fahrenheit (minus 62 degrees Celsius), according to FBI special agent Tom Simon in Hawaii.

The FBI said the plane eventually reached an altitude of 38,000 feet (11,582 meters), where oxygen is so scarce that survival is difficult.

The only way the teenager could have lived through such a journey was for his brain to cool down enough to require only a low level of oxygen, but not enough for his heart to stop beating, said Peter Hackett, director of the Institute For Altitude Medicine in Colorado.

"It's all a little hard to believe, but that's the explanation," Hackett said.

Since 1947, 105 people worldwide have been found to have stowed away on flights, and 80 of them died, according to the Federal Aviation Administration. That represents a survival rate of less than 24 percent. The last known stowaway to walk away from such an ordeal was in 2013 on a domestic flight in Nigeria.

The teenage stowaway to Hawaii randomly chose a plane to climb into at the airport in San Jose, with no specific plan to make the treacherous flight to Hawaii, Simon said.

No one answered the door at a home believed to be the teenager's residence in Santa Clara. There has been conflicting information about his age. Simon said he was 15, while Rosenfeld said her agency has information showing him as 16.

If Hawaii officials do not determine the boy suffered any abuse or neglect back home in California, the Santa Clara County Social Services Agency would typically not become involved in the case, said Stanley Lee, a spokesman for that agency. – Reuters