Colombia's navy made the largest drug seizure in the nation's history when it uncovered up to 27 tons of cocaine buried along the Pacific coast, the defense minister said Monday.

The cocaine, with a wholesale value of more than $500 million, was found Sunday buried in 1,000 packages of 55 pounds each near the coastal town of Pizarro, 250 miles west of Bogota, Defense Minister Juan Manuel Santos told a news conference.

Later, Navy Adm. Guillermo Barrera told The Associated Press by telephone that 919 packages of cocaine had been found. The different numbers could not be immediately explained. The figures put the cocaine seizure between 24 tons to 27 tons.

Santos said the seizure was the result of eight months of undercover police work and he called it the "biggest in the history of Colombia."

The cocaine was buried near an estuary accessible only by sea, he said.

There were no arrests in the operation, but the drugs were believed to belong to Colombia's biggest drug trafficking organization, the Norte del Valle cartel, which operates near the area.

The seizure came as President Alvaro Uribe travels to Washington on Tuesday to shore up support on Capitol Hill and the White House for the U.S.-backed Plan Colombia, an anti-narcotics and counterinsurgency program that has cost American taxpayers more than $5 billion since 2000.

Colombia is the world's leading cocaine producer, producing annually more than 500 tons of cocaine that represents 90 percent of the drug consumed in the United States.

Most of the cocaine leaves the country by sea, on go-fast boats that transport the drugs up along the Central American coast for their eventual smuggling into the United States overland through Mexico.

Although drug seizures are an everyday affair, they rarely reach such large numbers. Last October, Colombia's navy made headlines when it found 9.3 tons of cocaine on three go-fast boats near the Pacific coastal port city of Buenaventura — its biggest seizure of the year.