Nigeria has not concluded its investigation into what caused a plane crash in June that killed 163 people, the accident bureau said on Sunday, despite the government lifting a ban on the airline this week.

The Dana Air flight, a McDonnell Douglas MD-83, smashed into an apartment block in a populated Lagos suburb in June, killing everyone on board and 10 people on the ground, according to a preliminary government report.

The aviation ministry on Wednesday lifted a suspension of the operating license of the privately owned Nigerian airline, saying it was satisfied with its air-worthiness following an audit.

"I can not be specific on the time that the final report would be ready," Commissioner of the Accident Investigation Bureau (AIB) Muktar Usman told Reuters.

"Every process that needs to be done for the conclusion of investigation is being followed. It will be ready soon."

Air crashes are relatively common in Africa's second biggest economy, which has a poor air safety record.

A preliminary AIB report in July said the captain had reported dual engine failure, but did not say what caused it.

Relatives of the crash victims are furious, and are lobbying the government to suspend Dana until the inquiry is finished.

University professor Ifeoma Onyemelukwe broke down in tears as he recounted how he lost his youngest sister in the crash.

"We try to recover from the shock, then they bring back the airline like that when they don't even know what happened? They have no respect for human dignity. It's like chickens have been slaughtered," he said, adding that some relatives had not yet received bodies of their loved ones because of autopsy delays.

Dana said in a statement on Friday it was "continuing to offer complete cooperation ... in the investigation, and we will continue do so for as long as they require."

Most of those killed in the crash were Nigerians, although the dead included a family of six Americans of Nigerian descent, four Chinese, two Lebanese, a French woman and a British woman.

Among the dead was the spokesman for the state oil firm, Levi Ajuonuma, whose son Obinna is campaigning to shut Dana down.

"All of a sudden, the Federal Government decided to free Dana just like that," he told the local Daily Times. "There are no conclusions on (it), no court ruling, absolutely nothing."