BANGKOK, Thailand — A shipment of arms and apparently sophisticated missiles from North Korea seized here on a tip from American intelligence agencies has set off a series of investigations, as officials try to determine whether the cargo was headed to South Asia or the Middle East.

The Obama administration welcomed the interception by the Thai authorities as evidence that it had scored a success in its effort to enforce a United Nations Security Council resolution banning weapons exports by the North Korean government, an attempt to cut off the country’s most profitable export.

A senior White House official in Washington, declining to speak on the record because the interception on Friday had required high-level coordination among intelligence agencies that watched the shipment as it was loaded in Pyongyang, said the seizure was evidence that the administration would “aggressively and rigorously implement” the Security Council resolution, passed in June after North Korea set off its second nuclear test.

The resolution, No. 1874, authorizes any country to inspect and seize North Korean weapons shipments that pass through its territory, regardless of the cargo’s ultimate destination.

The Obama administration is trying to show that it will choke off the North’s illicit exports even while attempting to reopen nuclear talks. In interviews in recent weeks, several officials said they believed that the Bush administration, which came to office seeking to topple the North Korean government of Kim Jong-il, mistakenly eased pressure on him while pursuing disarmament accords, almost all of them since renounced by the North.

But on Sunday, United States officials were largely silent on the destination of the shipment, saying they were still trying to sort through conflicting reports and misleading flight plans.

One senior official said he believed that the shipment was headed to Iran, a major buyer of North Korean missiles and arms, some of them passed on later to Hezbollah or Hamas.

Others said they thought the more likely destination was Pakistan, which also has a long history of purchases from North Korea, but which has been under heavy American pressure to cut its ties to Mr. Kim’s government.

Thai officials arrested the five-man crew on Friday after seizing the large cargo craft at Bangkok’s military airport, where the crew had landed to refuel. It was unclear why the crew would have chosen a close American ally for a refueling stop, rather than neighboring Myanmar, which has deep business and political ties to North Korea.

Thai officials said they intended to charge the crew members with possession of weapons of war. On Monday, a court here approved a 12-day detention for the five men.

But in their first interview since they were arrested, the crew members insisted that they did not know they had been transporting an arsenal of at least 30 tons of missiles, grenade launchers and other weapons, some of which the Thai authorities were still trying to identify.

“They said it was oil drilling equipment,” said Viktor Abdullayev, the plane’s co-pilot.

“That’s what the manager told us,” he said, referring to the crew’s employer, a civilian cargo company from the former Soviet republic of Georgia.

Mr. Abdullayev and his colleagues said they started their trip in Ukraine, picked up cargo in North Korea and were traveling back to Ukraine via Thailand, Sri Lanka and the United Arab Emirates. They declined to say in which of those locations the cargo was meant to be delivered. The emirates, officials note, are often used as a transit point to Iran.

Mr. Abdullayev said it never occurred to him to ask about the cargo. “I have no interest in what I carry,” he said. “Like a truck driver: just keep driving.”

An intriguing hint about his cargo came from a photograph published in Thailand. It showed a series of rockets stacked in the cargo hold, with the crates marked “K 100.” The rockets were visible, though partly shrouded. Numbers on individual crates that ran in sequence — like 78, 83, 86 and 87 — presumably denoted the individual weapons in the shipment.

Charles P. Vick, a missile expert at GlobalSecurity.org, a research group in Alexandria, Va., said that if the markings were correct, the rockets might be K-100s, a type of Russian missile designed to destroy sophisticated radar planes. They are advertised as “Awacs killers,” a reference to the Airborne Warning and Control System planes used by the United States, Israel and soon India, which can orchestrate combat plans.

Mr. Vick noted that the diameter and length of the packaged missiles in the photograph appeared to match the specifications of the K-100: 16 inches wide and 20 feet long.

“It’s just a guess,” he cautioned.

But he said it was also possible that the tubular weapons might be smaller artillery rockets packed end to end to fit in the large metallic crates. Those types of rockets are “the kind of thing” that Hamas and Hezbollah use against Israel, he said.

Panitan Wattanayagorn, the Thai government spokesman, said in an interview that the aircraft, a Russian-made Ilyushin 76 registered in Georgia, passed through Bangkok twice — on its way to North Korea and on its return.

Four of the crew members are from Kazakhstan: Mr. Abdullayev, Ilyas Issakov, Aleksandr Zrybney and Vtaliy Shurmnov. The fifth, Mikhail Prtkhou, is from Belarus.

The aircraft was searched on the return journey after the Thai authorities were tipped off by American officials that it might be carrying weapons. The crew members were detained and the cargo was confiscated, but not immediately. The crew members had enough time to buy six large bottles of beer at a duty-free shop, but those were confiscated in the detention center where they have been kept since.

“There’s much more to this story than what has been made public so far,” said Bertil Lintner, an author who has written extensively on North Korea. “Why would you refuel in Thailand?”

Mr. Lintner said that if the aircraft had landed in neighboring Myanmar, which is ruled by generals friendly to the North Korean government, “there would have been no problem.”

No major seizures of weapons have been made public since the passage of Resolution 1874. This summer for about three weeks, the United States Navy tracked a North Korean freighter suspected of carrying banned cargo, and the ship eventually turned back to its home port without incident. The resolution does not permit the boarding of ships on the high seas.