The investigation by the Hawks began in earnest last month after a tip-off in January implicated apartheid-era government officials and security agencies, including the SA Defence Force, in engineering the crash.

A two-week investigation by The Times has revealed that an inquiry involving South African and Mozambican police, the National Prosecuting Authority and the Civil Aviation Authority started in November.

President Jacob Zuma is said to have sanctioned the inquiry, which is separate to that launched by the Justice Department.

Presidential spokesman Zanele Mngadi, whose office confirmed that the investigation had begun, referred questions to the Hawks.

Zuma's approval is believed to have been obtained on the strength of evidence obtained in September that includes documents, photographs and voice recordings.

The 15-member investigation team of South African and Mozambican police came into possession of the evidence as a result of the January tip-off.

The Times has learned that last week police crime scene experts took aerial photographs and GPS (global positioning satellite) readings in a restricted military zone at Mariepskop, Mpumalanga.

Radar installations in the zone feed aerial intelligence data from across Southern Africa to South African Air Force bases .

Mariepskop, near God's Window, is close to Mbuzini, where Machel's plane crashed, killing him and 24 others. Nine people survived.

The Times' source said: "Numerous reports from the Margo Commission of Inquiry are being reviewed, along with photographs and transcripts of flight voice data, and air traffic control recordings."

In 1987, Judge Cecil Margo exonerated South Africa of involvement in the crash and cited pilot error as the cause.

Russian experts concluded that the crash was caused by the crew being misled by signals from a decoy navigation beacon that transmitted more strongly than the beacon at Maputo airport.

In 1994, the cause of Machel's death was the subject of a closed Truth and Reconciliation Commission inquiry, which said it had evidence that linked the crash to the SA Defence Force.

NPA spokesman Makhosini Nkosi yesterday referred all questions to the Hawks.

Hawks spokesman Captain Paul Ramaloko confirmed the investigation.

"We are working with our Mozambican counterparts."

Mozambique embassy police attache Zachery Cossa said the embassy was aware of the investigation.

Civil Aviation Authority spokesman Phindiwe Gwebu said the authority was involved in the investigation.

An aviation source said: "The possible roles of certain people have been identified. Those alive cannot be allowed to escape justice like those who have died."

Dumisa Ntsebeza, the advocate who led the TRC investigation, said he had been approached by the Hawks.

"I was asked to reactivate my team. I told them if they had the budget we could. I have heard nothing from them since."

Ntsebeza said the investigation should have been done 14 years ago "when we told the Justice Department what needed to be done".

"We handed over 43 files of documents pertaining to murders, which we were unable to fully investigate because of time constraints. Among those files was this case," he said.

" Those documents contain detailed information, including a sworn statement by a military intelligence agent involved in setting up the false beacon.

"This agent gave detailed accounts of a meeting held the day before the crash, where this was planned. He gave names of those at the meeting, held at the former security police base Skwamans, close to the crash site. The next day these people were the first on the scene.

"Among those there were ministers and top military brass, including Pik Botha, defence force chief General Kat Liebenberg (who died from cancer in the 1990s), and military intelligence chief General Joffel van der Westhuizen."

Ntsebeza said: "What we discovered justified further investigations, including that the South African government was not 'uninvolved'.

"People die, memories fade, documents [get] lost and time [is] gained to cover tracks. If Samora Machel was lured to his death on South African soil it is a crime and a proper criminal investigation should have been conducted."

Ntsebeza said the Justice Department had a duty to prosecute those linked to the crime.

He said Machel's wife, Graca, told the TRC of a crisis meeting in Malawi, in February 1984, convened after Machel threatened to close Malawi's sea access if it did not stop helping Renamo.

"The possibility of assassinating Machel was allegedly discussed at this meeting. The following week, Malawi's president sent officials to meet President PW Botha, who sent a message of solidarity to Malawi through a delegation headed by Magnus Malan [the South African defence minister].

"It was Graca Machel's belief that the meeting discussed the formation of a special team to monitor Machel's movements. [Machel] was under enormous pressure at the time of his death, even from his own party. Graca Machel, a member of Machel's cabinet, confirmed [that there had been] attempts on his life at his residence, and South Africa's attempts to attack Maputo.

"Machel, at the time of his death, was engaged in a radical restructuring of his government and military, which could have upset a number of high-ranking Mozambicans."

Defence analyst Helmoed Heitman questioned the launching of the investigation.

"If the South African government wanted to kill Machel, there were simpler ways of doing it. I was privy to a briefing by a team of air force investigators ... certain allegations that the pilots were drunk were incorrect ... the crash's cause pointed to human errors, miscommunication and crew arrogance in terms of ignoring numerous warnings.''

Former foreign minister Pik Botha yesterday welcomed the new investigation.

"But only as long as it, like the Margo Commission, includes international air crash investigation experts. People forget that the [Margo investigation] also consisted of experts from the UK and US."

Responding to suspicions raised at the truth commission about his quick arrival at the crash scene, Botha said: "The commission came to the finding that South Africa was not involved - not me and not the government. As to my quick presence on the scene, this is [in accordance] with international protocol. I was never questioned over it then. I don't mind being questioned now," he said.

He questioned whether the truth commission had the expertise to reach its findings.