KAMPALA, Aug 19 (Reuters) - Both black boxes from the wreckage of the helicopter crash that killed Sudan's Vice President John Garang will be sent to Russia for analysis, investigators said on Friday.

Garang's death in Uganda's presidential helicopter stunned Africa, triggered riots and fed fears the peace deal he crafted with Sudan's Islamist government might unravel.

Sudanese investigator Abel Alier said the Russian-built aircraft's flight data recorder and cockpit voice recorder would be sent to the Russian aviation authority in Moscow, possibly as soon as Saturday.

"There they will ascertain the contents of the recorders and will bring back the results," Alier, a former Sudanese vice president, told a news conference in the Ugandan capital.

"We are trying to get all the available information."

Dennis Jones, a U.S. National Transportation Safety Board chief investigator and the lead technical adviser in the probe, said it would take about five days to study the black boxes and estimated the crash investigation could take about six months.

The investigators were addressing reporters after seven Sudanese officials arrived in Kampala to join the probe, a multinational effort involving officials from Sudan, Uganda, Kenya and the United States.

Heading Uganda's team, Minister of Works, Housing and Communication John Nasasira rejected a United Nations report that 17 bodies were found in the wreckage.

He said forensics experts from the United States, Kenya, Uganda and Sudan had all verified there were 13 bodies: seven Ugandans, Garang, and five other Sudanese.

"We have been trying to get a clarification from the U.N. on that, and we hope it will come soon," Nasasira said.

On Aug. 10, a U.N. spokeswoman in the Sudanese capital Khartoum said the remains of 17 people had been recovered.

Garang signed a peace deal in January to end Africa's then longest civil war in Sudan's south. His death triggered riots that killed at least 130 people in Sudan, mostly in Khartoum.

Ugandan Internal Affairs Minister Ruhakana Rugunda was one of the first people to visit the remote crash site in the mountainous border area between the two east African countries.

He denied local media reports that the bodies of Garang and the other passengers were found riddled with bullets.

"We did not find any evidence of bullet wounds when we jointly examined the bodies of the victims," Rugunda said.