(CNN) -- There is no evidence to suggest that the two men who used stolen passports to get aboard Malaysia Airlines Flight 370 had anything to do with its disappearance Saturday as it was flying from Kuala Lumpur to Beijing, an official said Tuesday.
"The more information we get, the more we're inclined to conclude that it was not a terrorist incident," Interpol Secretary General Ronald Noble told reporters Tuesday at his organization's headquarters in Lyon, France.
Here's what we know about what happened, how it happened and why.
WHO ARE THEY?
The passengers are Delavar Seyed Mohammad Reza, 29, and Pouri Nourmohammadi, 18.
They entered Malaysia on February 28 using valid Iranian passports.
CNN obtained an iReport photo of what appears to be the two men with two of their friends. Metadata from the photo indicates that it was shot with an iPhone at 8:20 p.m. the night before the plane departed. CNN has blurred the faces of the other two men to protect their identities.
To fly out of Malaysia, Reza and Nourmohammadi used passports that were stolen in Thailand, a booming market for stolen passports. The passports belonged to citizens of Italy and Austria.
"Thailand remains a robust venue for the sale of high-quality, false passports (which includes altered, stolen passports) and other supporting documentation," said Paul Quaglia, who has been working in the region as a security and risk analyst for 14 years.
The Italian, Luigi Maraldi, 37, told reporters he reported his passport stolen in August. The Austrian, Christian Kozel, 30, had his stolen in July 2013.
Authorities said they don't know how Reza and Nourmohammadi came to possess the passports.
HOW DID IT HAPPEN?
On Saturday, Reza used the Italian's passport; Nourmohammadi used the Austrian's.
According to Thai police, an Iranian man named Kazem Ali bought one-way tickets for the men, describing them as friends who wanted to return home to Europe. While Ali made the initial booking by telephone, Ali or someone acting on his behalf paid cash for the tickets, police said.
The tickets were purchased at the same time from China Southern Airlines in Thailand's baht currency and at identical prices, according to China's official e-ticket verification system Travelsky.
The ticket numbers are consecutive, implying they were issued together.
Both were for travel from Kuala Lumpur to Amsterdam via Beijing.
The ticket for the man who was using the Italian passport continued to Copenhagen, Denmark. The ticket for the holder of the Austrian passport ended in Frankfurt, Germany.
Nourmohammadi was hoping to emigrate to Germany. The Iranian's mother had been expecting him to arrive in Frankfurt and contacted authorities when he didn't show up, said Malaysian Inspector General of Police Khalid Abu Bakar.
"If you read what the head of Malaysia police said recently, about (Nourmohammadi) ... wanting to travel to Frankfurt, Germany, to be with his mother, (this) is part of a human smuggling issue and not a terrorist issue," Interpol's Noble said.
Interpol says the passports were recorded as stolen in its database. But no country had checked them against Interpol's list. Countries, not airlines, have access to Interpol's data, and many governments don't routinely check passports against the database.
WHY DID IT HAPPEN?
Phil Robertson, deputy director of the Asia Division of Human Rights Watch, has a plausible explanation.
"After the Green Revolution in Iran for human rights and democracy was crushed by Iranian authorities, there were many Iranians who fled to Malaysia," he told CNN's Kristie Lu Stout.
Many Middle Easterners don't need a visa to enter Malaysia, which makes it a common destination for those seeking to emigrate for any number of reasons.
But they can run into problems when they try to depart Malaysia for countries that do require visas. "A stolen passport can be one way to do it," Robertson said. "Unfortunately, this is quite common."
How do they get them?
"Often persons like this, if they are going to make a play to go to somewhere like Germany or other parts of Europe, they would need some sort of broker to help them make the arrangements," he said. "So it's very possible you could have some sort of migrant smuggling group that's involved with this."
CNN's Tom Watkins, David Williams, Shimon Prokupecz, Katia Hetter, Karla Cripps, Khushbu Shah, Jethro Mullen and Jim Sciutto contributed to this report.