(Fixes date in paragraph 3 to April 16)
By Miyoung Kim
SEOUL, April 24 (Reuters) - The body of a South Korean boy whose shaking voice first raised the alarm that a passenger ferry with hundreds on board was in trouble has been found, his parents believe, but a DNA test has yet to confirm the find, media said on Thursday.
His parents had checked his body and clothes and concluded he was their son, the Yonhap news agency said. The crew had told the children to stay put as the ferry sank.
The Sewol sank on April 16 on a routine trip from the port of Incheon, near Seoul, to the southern holiday island of Jeju. Investigations are focused on human error or a mechanical fault, with media saying the ship was three times overloaded, with cargo poorly stowed and inadequate ballast water.
Captain Lee Joon-seok, 69, and other crew members who abandoned ship have been arrested on negligence charges. Lee was also charged with undertaking an "excessive change of course without slowing down".
Of the 476 passengers and crew on board, 339 were children and teachers on a high school outing. Only 174 people were rescued and the remainder are presumed to have drowned.
The confirmed death toll on Thursday was 159, with many of those found at the back of the ship on the fourth deck.
The first distress call from the sinking vessel was made by a boy with a shaking voice, three minutes after the vessel made its fateful last turn, a fire service officer told Reuters.
He called the emergency 119 number which put him through to the fire service, which in turn forwarded him to the coastguard two minutes later. That was followed by about 20 other calls from children on board the ship to the emergency number.
"Save us! We're on a ship and I think it's sinking," Yonhap quoted the boy as saying.
The fire service official asked him to switch the phone to the captain, media said, and the boy replied: "Do you mean teacher?"
The pronunciation of the words for "captain" and "teacher" is similar in Korean.
Divers have been swimming through the dark, cold waters in the ferry, feeling for bodies with their hands.
"We are trained for hostile environments, but it's hard to be brave when we meet bodies in dark water," said diver Hwang Dae-sik.
Most of those who survived made it out on deck and jumped into rescue boats but many of the children did not leave their cabins, not questioning their elders as is customary in hierarchical Korean society. They paid for their obedience with their lives.
(Additional reporting by Meeyoung Cho; Writing by Nick Macfie; Editing by Paul Tait)