LOS ANGELES -- South Korean security officials screened a man with a bulletproof vest before he got on a flight to Los Angeles, but they never detected a banned smoke grenade concealed in his checked luggage with a cache of knives, handcuffs, a gas mask and other weapons, a U.S. official said Wednesday.
Yongda Huang Harris and his carry-on luggage were thoroughly searched, but authorities found nothing suspicious, and he boarded the flight, said a Homeland Security official briefed on the investigation. The official was not authorized to discuss the case publicly and spoke on condition of anonymity.
Mr. Harris, 28, was arrested in Los Angeles last week during a stopover on a trip from Japan after U.S. Customs and Border Protection officers noticed the bulletproof vest. A search of Mr. Harris' checked luggage uncovered the smoke grenade and an array of suspicious items, including leg irons, body bags, a hatchet, billy clubs, a collapsible baton, duct tape and a biohazard suit.
U.S. officials were working with South Korean authorities to determine how the grenade slipped through screening.
Mr. Harris is not cooperating with federal officials trying to determine why he was headed to Boston with the weapons cache, authorities said. The smoke grenade was X-rayed by police bomb squad officers, who said the device fell into a category prohibited on board passenger aircraft.
Former Transportation Security Administration Deputy Administrator Tom Blank said the United States will likely scrutinize whether the failure to detect the grenade on a U.S.-bound jet was a one-time lapse or part of a wider security vulnerability. If the United States determines that another nation's airport doesn't meet U.S. standards, it can ask for stronger security measures and even bar flights directly to the United States from that country.
"This clearly looks like an error," Mr. Blank said of the grenade. "Something slipped through that should not have slipped through."
Many of the other belongings authorities say they found in Mr. Harris' luggage -- including the hatchet and knives -- wouldn't violate TSA guidelines for property in checked luggage. Also, bulletproof vests and flame-resistant pants such as the ones Mr. Harris was wearing aren't listed among prohibited items aboard flights.
There is no indication that Mr. Harris, who does not have a criminal record, is linked to a terrorist organization or planned to damage the plane, and it's unlikely that a smoke grenade could bring down the aircraft, the federal official said. But the smoke grenade is banned from planes under the United Nations' explosives shipping rules. Depending on conditions when ignited, the grenade could fill the cabin with smoke or cause a fire, officials said.
Customs officers believed that the lead-filled, leather-coated billy clubs and collapsible baton might be barred by California law, according to an affidavit filed in U.S. District Court.
Increased airline security after 9/11 sought to armor flights against terrorist threats, but they can also test credulity for those getting on board. An intrusive pat-down by security or discovery of a too-big bottle of tanning lotion can leave a passenger feeling violated, while Mr. Harris -- outfitted in a bulletproof vest, flame-retardant pants and knee pads underneath a trenchcoat, with a concealed arsenal in his luggage --appears to have triggered no suspicion before arriving in Los Angeles.
"The one thing that concerns me is he was able to board a plane internationally with all these weapons and whatnot, and nobody in Japan, nobody in Korea, bothered to find these things until he got to America," said Gadisa Goso, 29, a school administrator and neighbor of Mr. Harris' mother in Boston. "That's a big concern for, like, for the U.S."
Mr. Harris has been charged with one count of transporting hazardous materials, an offense that carries a maximum penalty of five years in prison. He made a brief court appearance Tuesday, but his arraignment was delayed until Friday, and he was ordered held until then.
Mr. Harris is a U.S. citizen whose permanent residence is in Boston, though he recently started living and working in Japan, officials said.