While nearly every aspect of this weekend’s disappearance of a Malaysian jetliner is surprising, one element is not. At least two of its 239 passengers had been traveling with stolen passports — and those documents had been lost in Thailand, home to what’s become one of the most robust stolen passport trades in the world.

Italian Luigi Maraldi, left, whose stolen passport was used by a passenger boarding a missing Malaysian airliner, shows his passport as he reports himself to Thai police at Phuket police station in Phuket province, southern Thailand Sunday, March 9, 2014. Maraldi spoke at a police news conference where he showed his current passport, which replaced the stolen one, and expressed surprise that anyone could use his old one. (AP Photo/Krissada Muanhawang)

Both Luigi Maraldi, a short-haired Italian, and a 30-year-old Austrian named Christian Kozel had been traveling through a southern province in Thailand called Phuket when their passports were lost — or stolen.

In 2012, Kozel’s went missing in Phuket, which juts out of Thailand’s main coast like a snaggletooth. And on July 22 of last year, someone took Maraldi’s after the Italian submitted his passport as collateral on a rented motorbike, by far the most used means of transportation in Southeast Asia.

INTERPOL confirmed in a statement Sunday night that at least two passports – Austrian and Italian – recorded in its Stolen and Lost Travel Documents (SLTD) database were used by passengers on board missing Malaysia Airlines flight MH 370. An INTERPOL statement said that:

“No checks of the stolen Austrian and Italian passports were made by any country between the time they were entered into INTERPOL’s database and the departure of flight MH 370. At this time, INTERPOL is therefore unable to determine on how many other occasions these passports were used to board flights or cross borders,” the statement said.

It’s unclear why or how Maraldi and Kozel’s passports wound up on the vanished Malaysian jetliner, or if the passengers who possessed them were terrorists or somehow involved the plane’s disappearance. Thai police, who say they’re investigating a “passport ring,” interviewed Maraldi on Sunday. He couldn’t fill in any more details. “I really don’t have much to add,” Maraldi told the South China Morning Post. “I am not an expat who lives on Phuket. I have come and gone as a tourist.”

Which is exactly what made him so susceptible. The theft of his passport reflects broader trends. Many motorbike rental shops will only allow a tourist to take a bike if he or she deposits their passport as collateral. Most passports make their way back to their owner, but some do not. When Maraldi asked for his back at a bike shop hugging Phuket’s western coast, the owner told him she’d forked it over to an Italian who’d “said Mr. Maraldi was his husband.”

Message boards from Lonely Planet to Thai Visa are clogged with accounts of stolen passports or ruminations on whether to leave their own at a bike shop. New Zealand, which sends thousands of tourists to Southeast Asia every year, warns its travelers to never leave their passports with a motorcycle rent shop — because no one knows where they could wind up.

Six Syrians, who were caught carrying fake Greek passports, have been held in Phuket International Airport for weeks, the region’s English-language newspaper Phuketwan reports.

“The counterfeiting of all sorts of identifications is very widespread particularly out of Thailand,” Steve Vickers, a Hong Kong-based risk consultant, tells the Wall Street Journal. “So it’s pretty easy to pick up a stolen or a counterfeit passport.”

According to Australian Consul Larry Cunningham, the theft of passports in Thailand — and especially in Phuket — is a “regular occurrence.” ”Some passports were certainly lost, falling out of pockets or being genuinely misplaced,” former Australian consul Larry Cunningham told the South China Morning Post. “But there were also substantial incidents of passports being stolen.” He told the newspaper that thieves sometimes break into rooms and lift passports for sale on the black market, where they disappear.

And, perhaps, wind up on a plane that disappeared somewhere off Vietnam’s southern coast.