French customs officers are inspecting a North Korean ship at an Indian Ocean island off the coast of Africa as part of U.N. measures prompted by the communist nation's nuclear test, but they found nothing illegal so far, officials said Thursday.

The inspection, which began Saturday while the ship was docked at the island of Mayotte, appeared to be the first time French officials have examined a North Korean ship since the United Nations passed a resolution last month calling for searches of cargo entering and leaving North Korea as a result of its Oct. 9 nuclear test.

It was not immediately clear whether any other countries have carried out similar inspections.

A customs official in charge of maritime inspections on Mayotte said the 500-foot-long Am Noenok Gang, with 45 crew members, had been searched "from bow to stern and top to bottom." The inspectors found a slight excess of alcohol and cigarettes but "nothing really illegal, in terms of weapons or drugs," said the official, who asked not to be identified because he was not authorized to speak to the media about the inspection.

He said the ship was heading from Singapore to the Comores Islands, also in the Indian Ocean, with a stop in Mayotte. The ship was transporting cement.

The inspection is "going very well" and the North Korean crew "are very nice," he said.

Customs and police officers first inspected the vessel at sea when it arrived in Mayotte's waters last weekend, he added. It was only the second North Korean boat in five years to dock in Mayotte, he said.

A French diplomat said the inspection started with a routine identity check Saturday. Inspectors decided to unload all the merchandise, and will continue checking the ship through the weekend, he said on condition of anonymity because of the sensitivity of the issue.

He said the inspection was slowed because the port on Mayotte is so small that the ship had to clear out several times to make way for other vessels carrying perishable cargo.

The Mayotte customs official said some of the boat's load of cement was destined for use on the island, with the rest going to the Comores.

The U.N. resolution is aimed at keeping North Korea from importing or exporting nuclear equipment or technology.

"The customs administration is currently proceeding with a complete and thorough inspection of merchandise and personnel on a North Korean ship on a stopover in Mayotte," Foreign Ministry spokesman Jean-Baptiste Mattei said.

Mayotte is a French-administered island between the east coast of Africa and Madagascar.

"We are exercising particular vigilance regarding cargo transported by North Korean ships, and all ships starting from or heading to North Korea," Mattei said.

The announcement came as President Bush warned North Korea against transferring nuclear weapons or material to other countries, saying such an act would be considered a "grave threat" to the United States.

South Korea balked this week at fully joining the U.S.-led effort to intercept North Korean ships. Countries in the initiative can only conduct searches within the territorial waters of participating countries, since ships on the high seas have right of free passage under international law.

After the nuclear test, France took immediate measures limiting visas for North Koreans and canceled all bilateral contacts in October and November, Mattei said.