PORT BLAIR, India (Reuters) — Indian authorities were inspecting a North Korean ship detained in the Bay of Bengal for nuclear material or fuel, officials said, the latest sign of the international noose tightening around the North.

A preliminary investigation by a team of nuclear scientists failed to detect any radioactive presence on board the ship carrying a huge sugar consignment, Ashok Chand, a senior police officer in India's Andaman and Nicobar islands, told Reuters.

"There will be more checking today and we will open the hatch to check the entire consignment for any radioactive material," Chand said.

The MV Mu San dropped anchor off Hut Bay island in the Andaman Islands last week without permission and was detained by the coastguard after a more than six-hour chase.

UN member states are authorised to inspect North Korean sea, air and land cargo, and seize and destroy any goods transported in violation of a Security Council resolution in June following the North's nuclear tests.

"India is strictly following the rules and has the right to ask ships to be inspected to ensure that they are in compliance with the UN resolution," said Uday Bhaskar, Director of the National Maritime Foundation, a New Delhi-based think tank.

North Korean sales of missiles and other weapons materials to tense or unstable parts of the world have long been a major concern of the United States and its allies.

Indian officials said they were trying to find whether the MV Mu San was anywhere near Myanmar, which is suspected to be seeking help from North Korea to build a nuclear reactor.

A former Indian diplomat said New Delhi was wary of a possible North Korea-Myanmar nuclear cooperation and had therefore stepped up security near the Andaman Islands, which is close to Myanmar.

"With increasing reports of North Korea helping Myanmar build a nuclear reactor, any vessel floating in Indian waters without a possible reason will be checked and India is rightly concerned," said Naresh Chandra, a former envoy to Washington.

A full interrogation of the 39-member crew can only begin after the arrival of a Korean interpreter later on Monday, officials said.

North Korea, which has walked out of six-party talks aimed at reining in its nuclear weapons programme, fired a barrage of short-range missiles in launch tests in May and exploded a nuclear device on May 25, resulting in tougher UN sanctions that it has ignored.

Experts say North Korea are feeling the blows from UN sanctions and could face more international pressure.

"North Korea is realising that the eyes of the world are on them and they are feeling the blows from UN sanctions," said Lee Sang-hyun, director of the security studies programme at the Sejong Institute think tank, located near Seoul.

"They will have to be careful because this incident shows that they are feeling more pressure from countries around the world," Sang-hyun added.