TOKYO — Japanese police said Monday that they have arrested 11 Chinese nationals in northern Japan for allegedly working at a construction site without passports or proper visas, and later discovered that dozens of fellow workers had fled.

Hokkaido police said the 11 Chinese, aged from 27 to 62, were arrested Nov. 26 near a train station in Kikonai town on the southwestern coast of Japan's northern main island. Police said two were without passports, while nine others allegedly overstayed their visas.

The workers were mobilized at a solar power plant construction site by a company near Tokyo, according to Japanese media reports. Officials were looking for 46 other Chinese who disappeared from the construction site after the arrests.

As fast-aging Japan faces serious labor shortages, the foreign work force has rapidly increased, sometimes illegally or under harsh working conditions.

Construction is a sector where workers are particularly needed as Japan accelerates the building of infrastructure to bolster tourism ahead of the 2010 Tokyo Olympics.

Japan is discussing legislation that would allow more foreign workers in construction, farming and other blue-color jobs — a major policy change. The country has long resisted accepting unskilled foreign workers.

Japan has a long-established internship program designed to offer mainly Asian workers on-the-job training, but often under poor conditions criticized by rights groups as forced labor. Last year, some 7,000 of the 270,000 technical interns fled, citing underpay and mistreatment, according to government statistics.