Calling the situation an "urgent matter," the Taiwanese government has asked U.S. authorities for more information about the mysterious circumstances surrounding the death of a Taiwan national four years ago in Honolulu.

Oliver Liao, deputy director of the consular division for Taiwan's de-facto embassy in Washington, D.C., said his government had serious concerns that it hadn't been fully informed about the case of Chen Chi Huang, who was found hanging in his federal jail cell in April 2003, a week after U.S. authorities detained him at Honolulu International Airport.

The Advertiser recently reported that Huang had been the target of a national security investigation at the time of his death, and that he had been questioned at the airport about nuclear-production documents reportedly found in his luggage upon arriving on a flight from Taiwan.

The newspaper learned of the investigation and the focus of the airport interrogation this month after obtaining federal records through a Freedom of Information Act request.

Taiwanese officials told The Advertiser they did not know about the national-security or nuclear-documents connection until the newspaper uncovered them.

The U.S. government previously had told Huang's government that he was detained for allegedly not having proper immigration paperwork.

"We are quite confused and concerned," Liao said, noting that the embassy sent a letter to the U.S. Department of Homeland Security following publication of The Advertiser story.

"We made it very clear we had real concerns about what happened."

The department has yet to respond, Liao said.

A Homeland Security spokeswoman said she could not reach anyone late yesterday to provide a comment.

The nuclear-documents angle and the many unanswered questions about the Huang case have attracted the attention of multiple media outlets in Taiwan and elsewhere abroad. Stories have appeared on at least a half dozen Web sites and on the pages of the two largest daily newspapers on Taiwan.

"It's a very, very big story," said Karl C.H. Kao, a Hawai'i-based reporter for the World Journal, a daily Chinese-language newspaper circulated in the United States, Canada and parts of Asia.

Kao has written three stories about the case, including one that ran on his paper's front page last week.

The intrigue has come from a variety of fronts.

Huang's relatives have disputed the U.S. government's finding that he committed suicide by hanging himself. They said his words and actions in the weeks prior to his death did not reflect a man intending to end his life. Huang, a frequent traveler between Hawai'i and Taiwan, came to O'ahu four years ago to visit his wife and three sons, who lived here and are U.S. citizens.

Huang's widow, Nicole Huang, declined comment yesterday.

The U.S. government also has contributed to the mystery. Differing from past practices in immigration cases, it did not notify the Taiwan government immediately upon Huang's detention but waited until after he was discovered hanging. Huang, who was rushed to a hospital in a coma, died four days later without regaining consciousness.

The news coverage in Taiwan and elsewhere also has generated questions about why the Taiwan government in 2003 didn't do an independent investigation into Huang's death, given the family's suspicions.

Taiwan is seeking more information now because of the new details that have come to light and because the government's job is to ensure the interests of its citizens are protected if detained in a foreign country, according to Liao.

The FBI earlier this month acknowledged that it had been investigating Huang at the time of his death, but it would not say whether the investigation was still open, citing national security. It also wouldn't say whether the nuclear documents reportedly found in Huang's suitcase were classified.

Huang told an immigration officer that he was given the documents by a friend, according to a transcript of his airport interrogation.

Liao said his government will try to get to the bottom of what happened.

"We are doing our best to seek the truth to make sure there was no wrongdoing on any side," he said.

Reach Rob Perez at rperez@honoluluadvertiser.com.