* Customs officials seized container at timber yard
* Investigation continuing, three people arrested
By Neil Marks
GEORGETOWN, Feb 20 (Reuters) - Drug enforcement agents in Guyana found 360 kg (794 pounds) of cocaine hidden in a shipment of timber destined for the Netherlands, one of the biggest ever seizures in the South American country, officials said on Wednesday.
Customs agents had been holding the container for more than a month at the Dutch-run Guyana Timber Products yard while they ran checks, and on Tuesday they drilled into the wood.
In total, 314 bricks of cocaine were found in seven of the logs when they were pried open. Three people were detained, the authorities said, including a Dutch national.
The Guyana Revenue Authority (GRA) said the timber had been inspected and certified by the state forestry commission, but that staff from its Drug Enforcement Unit noticed discrepancies between the paperwork and the container's contents.
"The GRA is continuing its investigation of any possible involvement by external agencies and the exporter in attempting to secret the substance in the logs," it said in a statement.
The country's biggest drugs bust was in 1998, when more than three tonnes - 3,154 kg (6,940 pounds) - of cocaine was found hidden in an empty fuel tank of a Panamanian-owned cargo ship bound for the Netherlands.
Guyana's political opposition has accused the government of not doing enough to tackle trafficking and violence linked to drugs gangs. The government rejects that and says it is working to strengthen the nation's security forces.
A U.S. diplomatic cable from 2007, published by WikiLeaks, says the United States was unable to advance on a proposal to open a Drug Enforcement Administration office in Guyana due to "lack of progress in addressing drug trafficking issues."
(Editing by Daniel Wallis and Cynthia Osterman)