LOS ANGELES >> A man dressed in a bulletproof vest and fire-resistant pants was arrested at Los Angeles International Airport after a smoke grenade, gas mask, leg irons and weapons were discovered in his luggage, federal authorities said today.

Boston-bound Yongda Huang Harris, 28, was arrested Friday on suspicion of transporting hazardous materials on a flight from Japan, U.S. Immigration and Customs Enforcement officials said.

Harris was not cooperating with federal officials attempting to interview him, according to a U.S. official who spoke on condition of anonymity to discuss an open investigation. The official said Harris is not believed to be linked to a terrorist organization, but his motive has not been determined.

Harris is a U.S. citizen whose permanent residence is in Boston, and he recently started living and working in Japan, officials said.

Harris has been charged with one count of transporting hazardous materials, an offense that carries a maximum penalty of five years in prison. Harris made a brief court appearance  today, and his detention hearing was postponed until Friday.

Harris’ retained attorney, Steven Seiden, was unavailable to comment, said Chris Williams, a spokesman for the lawyer.

It’s unclear what Harris had on his body and what he had checked in baggage, which will be crucial information to the defense, said Williams, who declined to comment on why Harris was carrying any of the weapons.

The defense attorney’s spokesman described Harris as “very intelligent,” earning A’s in high school and college calculus. Williams declined to elaborate on his background.

Harris drew suspicion when U.S. Customs and Border Protection officers at the airport noticed he was wearing the bulletproof vest and fire-resistant pants under his trenchcoat. That triggered a formal investigation by Homeland Security special agents.

A search of Harris’ checked luggage uncovered numerous suspicious items, including knives, body bags, a hatchet, a collapsible baton, a biohazard suit, a full-face respirator, billy clubs, handcuffs, leg irons and a device to repel dogs, authorities said.

The smoke grenade was subsequently X-rayed by the Los Angeles Police Department’s bomb squad. Officers said the device fell into a category that is prohibited on board passenger aircraft by the United Nations.

“Depending on the conditions when it is ignited, the smoke grenade, made by Commando Manufacturers, could potentially fill the cabin of a commercial airplane with smoke or cause a fire,” federal officials said in a news release.

Many of the other items in Harris’ luggage — including the hatchet and knives — wouldn’t violate Transportation Security Administration guidelines for what is permissible in checked luggage.

However, customs officers Kenny Frick and Brandon Parker believed in their initial investigation that the lead-filled, leather-coated billy clubs and a collapsible baton may be prohibited by California law, according to an affidavit filed in U.S. District Court.

Harris traveled from Kansai, Japan, to Inchon, Korea, before landing in Los Angeles.

Kansai airport police said they were not investigating and have not been asked to do so. It was unclear if any Japanese laws were broken since authorities there didn’t discover what was in Harris’ luggage, and therefore haven’t seen it.

Attempts to reach Harris’ family in Boston and his associates were unsuccessful.

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Spagat reported from San Diego. Associated Press writers Rodrique Ngowi in Boston, Eric Talmadge in Tokyo and Alicia A. Caldwell in Washington contributed to this report.