The guided missile destroyer USS Decatur intercepted the 40-foot boat on Monday. Aboard were a dozen men, three of them believed to have al Qaeda connections, and 3,780 pounds of hashish, the Navy said Friday.
"This is the first empirical evidence I've seen that conclusively links al Qaeda with the drug trade," said Bruce Hoffman, a terrorism expert at RAND, a think tank that often does work for the Pentagon.
The cargo is a possible sign bin Laden is using drugs to finance his war against America, reports CBS News Correspondent David Martin.
The Decatur seized the boat, a wooden vessel called a dhow, near the Straits of Hormuz, a narrow part of the Persian Gulf where it opens into the Arabian Sea. The area is a known smuggling route for al Qaeda, the Navy said.
The drugs are worth between $8 million and $10 million, the Navy said.
Military officials would not say Friday why they believed the boat, its cargo and some of its crew were linked to Osama bin Laden's terrorist network. The boat remained under the Decatur's control and it had not been determined what to do with the men on board, the Navy said.
Terrorism experts and government officials long have said they believe that al Qaeda makes money through criminal enterprises including the drug trade. A United Nations panel reported last month, for example, that al Qaeda had financed some of its operations through drug trafficking.
Before the Sept. 11, 2001, attacks, bin Laden had been sheltered in Afghanistan by the Taliban, which had clear links to the heroin trade through Afghanistan's huge opium poppy crops. Smaller groups linked to al Qaeda, such as Ansar al-Islam in Iraq and Abu Sayyaf in the Philippines, also have been accused of involvement in the drug trade.
But Hoffman said Monday's seizure was the first indication that al Qaeda was smuggling hashish, a drug made from the resin of marijuana plants that has a long history in the Middle East.
Smuggling drugs is attractive to al Qaeda because of the huge profit margins involved, said Jimmy Gurule, a former Treasury Department official involved in tracking terrorist financing.
"One of the things we learned over the past two years about al Qaeda is it's a very adaptable organization with respect not only to its terrorist activities but also its mechanisms for raising money," said Gurule, now a law professor at Notre Dame. "This isn't something that is a surprise, but it's something we should be prepared to address."
It's impossible to tell how deeply al Qaeda is involved in the drug trade, Hoffman said, because al Qaeda has become expert at hiding its money trail.
"Hardly anyone has a good handle on their finances," he said.
Congressional investigators said last week that authorities at both the Treasury and Justice departments were struggling to get a grip on how terrorists may be using alternative means - such as trafficking in gold and diamonds or drugs - to raise and move financial assets.
Terrorist financiers have been looking for ways to move and conceal money as governments in the United States and abroad have taken steps to prevent them from using the traditional banking system.
The Decatur is part of the Navy's effort to crack down on smuggling of drugs, weapons, oil and terrorists in the Persian Gulf.
The U.S. military also plans to sponsor a multinational exercise in the Arabian Sea next month to practice seizing a merchant ship carrying weapons of mass destruction. The scenario mimics the seizure of a shipment of Scud missiles from North Korea last year, which the U.S. eventually had to release to the buyer, Yemen.