U.S. Customs Service agents using blowtorches spent 30 hours ripping apart the belly of a Panamanian freighter before finding their version of a white Christmas: 4,792 pounds of cocaine hidden in a secret compartment.

The shipment, which was destined for holiday consumers, brought a five-day total of cocaine seized on two arriving freighters to 6,733 pounds, according to authorities, who said the shipments were from the same organization.The amount confiscated made it one of the largest cocaine busts in U.S. history, said authorities, who estimated the drugs' street value at $50 million.

"We had a little Christmas party," Customs spokesman Michael Sheehan said.

The latest bust came Tuesday after Customs agents, acting on a tip, spent the weekend staking out the Panamanian-registered freighter Santo Domingo Express, authorities said. The 300-foot ship, originating from northern Colombia, docked at the Miami River, Sheehan said.

No one appeared to unload the vessel, and agents boarded and seized the ship after the captain tried to leave port Monday, Sheehan said.

Agents were forced to open sealed compartments in the empty vessel's hold, where they found nothing, then spent 30 hours cutting through a ballast tank holding the cocaine, which was numbered, marked and stuffed into duffel bags, authorities said.

"This shipment was designed to be brought in during the holiday season," Woodrow Kirk, a Customs agent, told NBC News.

Initial evidence suggests the two shipments are related, said Sheehan, who did not elaborate on the theory.

"I don't care what anyone says, if you take 7,000 pounds out of any drug organization it's going to make a big dent," said Sheehan. The investigation was continuing, authorities said.

The captain, who was the only person aboard at the time of the seizure, was arrested on smuggling charges.