A Sudanese committee has been formed to investigate the death of vice-president and southern rebel leader John Garang, the government says.
John Garang symbolised southerners' hopes for 20 years
President Omar al-Bashir has asked for an initial report by the start of September, says Sudan's news agency.
The committee includes aviation experts, government officials and members of Mr Garang's former rebel SPLM group, the agency says.
Mr Garang's death sparked three days of rioting, which left more than 130 dead.
Mr Garang died with 13 others while returning to southern Sudan from Uganda when the Ugandan presidential helicopter flew into a cliff face.
Both the government and the SPLM have said it was an accident.
He died just three weeks after taking the post of vice-president under a peace deal ending 21 years of civil war.
Some analysts feared that his death could threaten the peace but all sides have pledged to stick to the agreement signed in January.
His successor as southern leader, Salva Kiir, is due to be sworn in as vice-president on Thursday - after a two-day delay.
All sides have pledged to stick to the deal John Garang signed
On Saturday thousands of people, including many African leaders, turned out to pay tribute to Mr Garang as he was buried in the southern town of Juba.
Mr Kiir assured mourners that the ex-rebel leader's vision of peace would not be allowed to perish.
"As sure as day follows night, the torch he has kindled shall not be extinguished. Not under my command," Mr Kiir said.