TAIPEI -- Prosecutors were investigating a Taiwanese company suspected of exporting to North Korea equipment that could be used in making nuclear weapons, an official said Tuesday.

The Yicheng Company, a Taipei-based import-export firm, is alleged to have transferred an industrial filtering device to North Korea earlier this year via China, said the official with the Justice Ministry's Investigation Bureau.

If proven, the transfer would violate United Nations sanctions and Taiwanese rules meant to punish North Korea for its nuclear programs. But the alleged deal also underscores budding commercial ties between economically poor, politically isolated North Korea and prosperous Taiwan, which has been marginalized in East Asian diplomacy by rival China.

The official declined to provide specifics about the filtering device but said it could be used in extracting plutonium to make nuclear weapons and also in making biological and chemical weapons.

"The equipment is on the embargo list for export to North Korea, as Taiwan follows the U.N. Security Council's trade sanctions," said the Investigation Bureau official, who spoke on condition of anonymity because he was not authorized to talk to the media.

Bureau investigators have handed the case over to prosecutors for further investigation and filing charges, the official said.

Yicheng could not be contacted for comment. The company's phone number is not listed publicly with the telephone company directory.

The U.N. Security Council imposed trade sanctions against Pyongyang in October 2006 after North Korea conducted its first successful nuclear test. Under the sanctions, all countries must prevent North Korea from importing or exporting any material for weapons of mass destruction or ballistic missiles.

The Investigation Bureau official said Yicheng would be the third company caught illegally exporting military-related equipment to North Korea this year.

In the two previous incidents, investigators found the Chenghui Co. sold equipment capable of manufacturing ammunition while Taipei-based Huayueh Co. exported computers with military uses.

The latest investigation comes amid progress in international efforts to get North Korea to abandon its nuclear programs. Pyongyang began this month to disable its sole functioning nuclear reactor and a related processing facility under a deal with the U.S., South Korea, China, Japan and Russia.

In return, North Korea is to receive the equivalent of 1 million tons of oil and other benefits from the five negotiating partners.