The privately owned Dana Air flight, a McDonnell Douglas MD-83, smashed into an apartment block in a densely populated Lagos suburb on Sunday afternoon, killing all 153 people onboard and an unknown number of people on the ground.

Because many bodies were fragmented or burnt beyond recognition, distinguishing the passengers from other victims has proven difficult, officials say.

"In circumstances like this it's difficult to be exact on numbers ... we have body parts that were not attached to anything," said Ade Ipaye, attorney general for Lagos state.

Only two bodies -- those of a woman clutching her child -- have been established to have been casualties on the ground.

However, authorities had done a survey of the building and the surrounding houses and found six people missing, said Oke Osanyintolu, of the Lagos State Emergency Management Agency.

He said this meant the death total might not exceed 159, but the final figure was not yet confirmed.

Workers have finished recovering bodies from the rubble, Ipaye said. In total, 149 bodies were found and a number of body parts.

Nigeria's government has suspended the air licence of Dana Air.

"Dana Air takes safety very seriously and our aircraft are sound," Dana Director Francis Ogboro told a news conference, repeating the firm's insistence that there was no mechanical fault with the plane before it went down.

On Monday search teams found the "black box" voice and data recorder, which the Accident Investigations Bureau says has been sent abroad for decoding.

Nigeria's historically poor air safety record had been improving, and Sunday's was the first big crash for six years.

Most of the dead on board were Nigerians, although an American family of six, of Nigerian descent, were killed, as were four Chinese citizens, two Lebanese and a French woman.

(Writing and additional reporting by Tim Cocks; Editing by Rosalind Russell)

• A Permanent Economic Emergency