An incinerator, where one of Africa's biggest hauls of narcotics is being burnt in Kenya, has exploded, delaying the process, police say.
Witnesses were not at risk, authorities said
No-one was hurt in the blast but it will now take 11 hours - three more than initially expected - as only one incinerator is working.
Police seized the 1.1 metric tons of cocaine worth $88m in December 2004.
The BBC's Karen Allen in Nairobi says the drugs are being destroyed to dispel fears they could be sold.
An official said the high temperatures reached by the bags of cocaine led the incinerator to malfunction.
"The exercise is going on smoothly despite" the blast, said director of public prosecutions Keriako Tobiko.
For the past few days, tests have been carried out on the cocaine seizure to prove that the sachets of drugs have remained intact.
Since the consignment was taken into police custody, speculation has been rife that some of the cocaine may have leaked out onto the international market.
Initial burning time: 8h 30mins
Weight: 1.1 metric tons
Seized: December 2004
The burning of more than 950 sachets of cocaine is being witnessed by foreign journalists, diplomats, members of the judiciary and suspects arrested for trafficking the shipments.
Some 200 policemen are also there to ensure security.
Officials say the witnesses will be not affected by the smoke and fumes coming from the incinerators.
Afterwards the residue will be buried in the grounds of Kenya's Medical Research Institute.
All week as part of a high security operation, tests have been conducted on the drug, closely monitored by international observers and in the coming weeks, more sophisticated forensic experiments will be carried out.
US officials were called in to inspect the drugs
The falling drug prices in the capital and a number of arrests of Kenyan Airways staff carrying cocaine into the UK had led to speculation that some of the consignment may have been sold.
Our correspondent says that despite evidence that the haul was not tampered with, some Kenyans remain sceptical about what they see as a public relations exercise.
Intelligence circles accept that drug cartels are now using Kenya to store their drugs - and that is only possible with protection from senior authorities, she says.