Special: 2014 South Korean ferry disaster Park officially apologizes for ferry disaster

SEOUL, South Korea - A civilian diver died Friday during the search for people still believed trapped inside a sunken South Korean ferry, the second diver's death in the six-week operation.

Government and civilian divers were mobilized after the ferry sank on April 16, leaving more than 300 people dead or missing.

A boom and a moan were heard via communication devices then fellow divers pulled the man to the surface as he fell unconscious, government task force spokesman Ko Myung-seok told a televised briefing.

The diver was bleeding on his face, received CPR and was taken to a hospital on a helicopter but was declared dead there, Ko said. The man whose surname was Lee was 46. His exact cause of his death wasn't known.

Ko said Lee was cutting open parts of the ship exterior to make searches easier. No bodies have been retrieved since May 21 as heavy objects like desks and cabinets have made it difficult for divers to navigate through unsearched parts of the ship, according to task force officials.

Since the sinking, 288 bodies have been recovered but 16 people are still missing. Only 172 people survived.

A 53-year-old civilian diver died earlier this month after becoming unconscious during a search attempt. He was pulled to the surface after losing communication five minutes into the search.

Officials have said they won't lift up the ship until family members of the missing people approves amid worries that works to hoist the ship may lead to damaging the bodies of those people.