SEOUL - Salvage workers who raised South Korea's sunken Sewol ferry found bone fragments on Tuesday believed to be from victims missing since the 2014 disaster, the maritime ministry said.

The wreck was brought to the surface last week in a complex salvage operation, nearly three years after it went down with the deaths of more than 300 people, and placed onto a semi-submersible ship that will finally bring it to shore.

Almost all the victims were schoolchildren and nine bodies were still unaccounted for, raising the prospect that they could still be inside the vessel and leaving their families emotionally trapped in the grieving process.

Six fragments of bone ranging in length from four to 18 centimeters were recovered on the deck of the semi-submersible Dockwise White Marlin, Lee Cheol-jo, a senior official in charge of the salvage operation, told reporters.

There was no indication whether they were from a single victim, or several individuals.

Officials from the National Forensic Service as well as the coast guard and the health ministry have been dispatched to identify the remains.

The operation to raise the 145-meter ferry has cost more than $82 million.

The salvage operation had been a key demand of the families of the nine missing victims - four schoolchildren, two teachers and a married couple and their child - who were moving to Jeju, the ship's destination, to start a new life.

Divers wrapped up their search in November 2014, and since then a handful of relatives set up home at Paengmok, a port an hour away from the accident site.

The sinking, one of the country's worst maritime disasters, dealt a crushing blow to now-ousted president Park Geun-hye.

Investigations concluded the tragedy was largely man-made - the cumulative result of an illegal redesign of the ship which made it top-heavy, an overloaded cargo bay, inexperienced crew and a questionable relationship between the ship operators and state regulators.