The crew of a cargo plane loaded with war weapons from North Korea was ordered Monday to remain in a Thai prison for 12 days for further investigations, as Thailand remained tightlipped about events leading to the aircraft's seizure and where it was headed. Thai authorities reportedly acted on a tip from their American counterparts when they impounded the Ilyushin 76 transport plane Saturday and discovered 35 tons of explosives, rocket-propelled grenades and components for surface-to-air missiles - a violation of United Nations sanctions against North Korea. Members of the five-man crew - four from Kazakhstan and one from Belarus - were charged Sunday with illegal arms possession and refused bail. Bangkok's Criminal Court on Monday approved a request from authorities to extend their detention by 12 days for further investigation, said police spokesman Pongsapat Pongjaren. The men, who declined comment to reporters at the courthouse, reportedly told investigators during a six-hour interrogation Sunday they believed they were carrying oil-drilling equipment and were not aware of any illicit cargo. Thailand's deputy Foreign Ministry spokesman Thani Thongphakdi said Monday he could not confirm conflicting local media reports about the plane's destination, with some saying it was headed to Sri Lanka and others saying Pakistan. He also declined comment on whether Thai authorities had ordered the plane to land or if the aircraft was intercepted during a refueling stop in Bangkok. "What I can say is that the actions that were taken were done pursuant to the UN Security Council resolution," Thani said, adding Thai authorities had been tipped off but he would not say by whom. "We had reliable information which led to the act." The latest UN sanctions - which ban the transport of certain weapons from or to North Korea - were imposed in June after the reclusive communist regime conducted a nuclear test and test-fired missiles. The sanctions were aimed at derailing North Korea's nuclear weapons program, but also banned the North's sale of any conventional arms. The seizure came just days after US President Barack Obama's special envoy made a rare three-day trip to North Korea on a mission to persuade Pyongyang to rejoin six-nation nuclear disarmament talks. Envoy Stephen Bosworth said the two sides had reached common understandings on the need to restart the talks. "There is a possibility that the incident could have a negative effect on moves to get the North to rejoin the six-party talks and a US-North Korea dialogue mood," Yang Moo-jin, a professor at Seoul's University of North Korean Studies, said Sunday. North Korea has been widely accused of violating United Nations sanctions by selling weapons to nations in Africa, Asia and Latin America. According to Thai Air Force spokesman Capt. Montol Suchookorn on Sunday the chartered cargo plane originated in North Korea's capital, Pyongyang, and requested to land at Don Muang airport to refuel. US Embassy spokesman Michael Turner said the embassy would not comment on if Americans had tipped off Thai authorities. Deputy Prime Minister Suthep Thaugsuban called a Monday meeting of Thailand's National Security Council to discuss the case. He said it would take several days to obtain details on the incident, which would be reported to the United Nations, Belarus and Kazakhstan. "People should not be alarmed because the government will ensure that the investigation will be carried out transparently. The government will be able to explain the situation to foreign countries," Suthep said Sunday. Thai authorities said the weapons were moved by trucks amid high security Saturday night from the airport to a military base in the nearby province of Nakhon Sawan. Baek Seung-joo of the state-run Korea Institute for Defense Analyses said the seizure demonstrated a US intention to continue to enforce sanctions on the North while also engaging in dialogue. Arms sales are a key source of hard currency for the impoverished North. Baek said the North is believed to have earned hundreds of millions of dollars every year by selling missiles, missile parts and other weapons to countries like Iran, Syria and Myanmar. In August, the United Arab Emirates seized a Bahamas-flagged cargo ship bound for Iran with a cache of banned rocket-propelled grenades and other arms from North Korea, the first seizure since sanctions against North Korea were ramped up.