LOS ANGELES — A 28-year-old man on a plane from Japan was arrested in Los Angeles after he was found wearing body armor and flame-proof pants, and transporting a small arsenal of weapons, officials said Tuesday.

Yongda Huang Harris, a naturalized US citizen of Chinese descent, faces a charge of transporting hazardous materials after he was detained by border guards Friday at Los Angeles International (LAX) airport.

Harris, who has lived in Japan recently and who was heading for Boston, was "wearing a bulletproof vest and flame retardant pants underneath his trench coat," said a US Immigration and Customs Enforcement (ICE) statement.

Further investigation of his checked luggage turned up a "pyrotechnic smoke grenade," along with a hatchet, knives, a gas mask, biohazard suits and body bags, it added.

Agents also found three leather-coated billy clubs, a collapsible baton, a full-face respirator, leg irons and a device to repel dogs, according to an affidavit by officers with Homeland Security Investigations (HSI), a division of ICE.

Bomb squad officers X-rayed the smoke grenade, and found that the "device fell under the United Nations' explosives shipping classification, meaning it is prohibited on board passenger aircraft.

"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," the ICE statement said.

Investigators are coordinating with counterparts in Tokyo, it said, adding that Harris has a permanent home in Boston, but "has been living and working recently in Japan."

He was due to appear in court in Los Angeles later Tuesday, and could face up to five years in prison.