Port Harcourt, Nigeria ? Investigators on Sunday picked over the scorched wreckage of an airliner that was ferrying schoolchildren home for the holidays when it crashed, killing all but three of the 110 people on board.

The cause of the crash was still unknown a day after the Sosoliso Airlines’ McDonnell Douglas DC-9 slammed into the ground on approach to the southern oil-industry center of Port Harcourt.

Among those on board were 71 teenagers from a Jesuit school in the capital, Abuja.

It was the second major air accident in seven weeks in Africa’s most-populous nation, and President Olusegun Obasanjo promised Sunday to overhaul Nigeria’s civil-aviation structures.

Airport officials directed frantic family members to local morgues. At one overwhelmed hospital, bodies were heaped together due to lack of space.

The wreckage lay Sunday in two principal parts several hundred yards apart, with investigators picking through the pieces in search for clues.

Tommy Oyelade, an Aviation Ministry official, said the plane’s flight-data recorders had been recovered.

The weather was stormy around the airport at the time of the crash, National Civil Aviation Authority spokesman Sam Adurogboye said.

The Paris-based aid agency Medecins Sans Frontieres said two of its international employees were among the dead: a French national and an American.