NIIGATA, Japan -- A North Korean ferry long suspected of smuggling missile parts and illicit funds arrived in a Japanese port amid noisy protests Thursday, but it was cleared by customs and safety inspectors.

Dozens of demonstrators watched by riot police chanted slogans denouncing North Korea's communist regime and protesting the North's kidnapping of Japanese as the Mangyongbong-92 slid into its berth in the northern port of Niigata for an overnight stay.

It was the second visit by the ferry -- the only passenger ship sailing between North Korea and Japan -- since its operator resumed service following a seven-month hiatus.

North Korea's supporters call the ferry, which has linked the two Asian neighbors for 40 years, a humanitarian lifeline. But some Japanese say the ship's visits aid the survival of a Stalinist regime that should be toppled.

Service was suspended after Japanese authorities vowed to tighten inspections of the ship, believed to be an important conduit for money and materiel needed to support North Korea's authoritarian regime.

But more than 100 customs, immigration and safety officials who marched up the vessel's gangplank Thursday afternoon found no irregularities, said Yoriaki Aoki, a spokesman for Japan's Transportation Ministry.

The ferry's departure from Niigata after its last visit Aug. 25 was delayed for nine hours after authorities drew up a list of five safety violations. Inspectors spent three hours Thursday verifying that all those glitches, including substandard firefighting equipment, had been rectified.

Another transport official, Ryoichi Sonoda, told reporters that the ship's operators had made a "serious effort" to bring the 11-year-old vessel in line with safety standards.

The ferry was expected to leave on schedule this morning with about 200 passengers, mostly ethnic Koreans living in Japan. It also will carry 100 tons of cargo including food and delicacies believed to be intended for celebrations Sept. 9 of the anniversary of North Korea's founding.

The Mangyongbong arrived in Niigata on Thursday afternoon to cheers from flag-waving North Korean residents and jeers by supporters of five Japanese who spent more than two decades in captivity in the North after being kidnapped for intelligence purposes.

Grass-roots groups believe more than 100 Japanese may still be held in North Korea after being kidnapped in the 1970s and 1980s.