Last week authorities in Kazakhstan announced that a container holding cesium-137, a radioactive material, disappeared, possibly after falling off a truck.

Details of the incident are sparse. The Kazakh government says it is searching for the container, which weighs over 100 pounds, but would not or could not say where it came from or where it might be headed.

It’s unclear how big of a threat the missing cesium poses, but experts say it highlights a growing global problem: As radioactive materials proliferate throughout the world, including in countries that don’t have the resources to secure, track or find them, there’s mounting fear that they could find their way into the hands of criminals and radical groups who could use them to build radioactive weapons, often referred to as dirty bombs.

“There’s concern that these sources are widely spread and easily accessible,” said Andrew Bieniawski, vice president of material security and minimization at the Nuclear Threat Initiative and a former top official in the U.S. National Nuclear Security Administration. “They’re used in everything from oil wells to the medical industry. You have thousands of these sources around the world, and people don’t realize they’re a threat.”

Analysts believe the radioactive material in Kazakhstan fell off a truck transporting it in the western part of the country. Tom Bielefeld, a German-based physicist and nuclear security analyst says the cesium likely came from an industrial source, possibly from a tool used in the oil industry to measure well depth. But it could also be related to Kazakhstan’s decommissioned BN-350 nuclear reactor.

In either case, the cesium probably has relatively low levels of radiation compared with other sources, according to experts. But that doesn’t mean its disappearance poses no threat. If even low-level radioactive sources are removed from their containers, they could pose serious threats to human health.

Bielefeld and others say regardless of the threat — or lack thereof — posed by the missing container in Kazakhstan, the incident shows that despite an increased global push to secure radioactive material, the risk it poses remains present in virtually every country on earth, including the U.S.

Radioactive materials are increasingly used in diverse industries, from oil wells to dentists’ offices — and those materials go missing from with surprising regularity.

The International Atomic Energy Agency (IAEA) reported about 140 cases of missing or unauthorized uses of nuclear and radioactive materials in 2013. But it’s likely that the number of cases is higher, as many cases go unreported, according to Bruce Bennett, a defense analyst at the Rand Corp.

“I don’t think we have a full accounting of everything worldwide,” he said. “Dentists don’t have armed guards patrolling their X-ray machines, and if a dentist’s office gets raided, it may not even make the news.”

The vast majority of the radioactive material that goes missing isn’t used in criminal activity, and the criminal use of radioactive material has been trending downward over the last decade, according to the IAEA.

The incidents know no borders. Radioactive material has gone missing everywhere from Uzbekistan to the U.S. While experts believe the threat posed by missing radioactive material is larger in less developed countries, where governments often lack the resources to track and find the missing material, more developed countries like the U.S. are nonetheless at risk.

For example, a 2012 congressional panel found that hospitals in the U.S. were failing to secure radioactive materials used in medical procedures and not thoroughly checking the backgrounds of employees who handled the materials.

This year has seen several high-profile cases in which radioactive material was stolen: one in Mexico in July and another that month in a section of Iraq controlled by the armed group Islamic State (IS). The missing material in Iraq likely poses little threat, according to U.S. officials, but experts say IS territory may become a hot spot for stealing radioactive materials.

“A big, nasty terrorist organization in control of swaths of land including science labs and such — that’s scary,” said Matthew Bunn, a professor at Harvard University's Belfar Center for Science and International Affairs.

Part of the fear among radioactive-material experts is that even people with little knowledge of the materials could make an incendiary device that would spread radioactive particles far and wide.

While a makeshift bomb would likely not be able to kill a large number of people, he said it could still cause substantial economic and social damage to an area. Because of that, he said it’s important to educate people about the risks of nuclear radiation.

“Most of the danger comes from the economic cost and from need to disrupt an area and evacuate people,” he said. “But educating people on the risks of radiation is very hard. People don’t pay attention until something happens.”

Governments around the world have been working on disseminating information about radiation risk and implementing better tracking systems for radioactive material. But the scale of coordination between countries required to strengthen those programs makes the process slow, he said.

The U.S. and 26 other countries still haven’t ratified a 2005 amendment that would expand a treaty meant to oversee international transport of nuclear materials to the domestic transport and storage of nuclear materials.

Without ratifying that amendment, Bunn and others say it will be hard for the U.S. to convince other countries to take the threat posed by nuclear and other radioactive materials seriously.

“The U.S. and [President Barack] Obama were trying to take the lead in securing nuclear material around the world,” Bunn said. “Yet we’re completely failing to take part in the legal instruments necessary for nuclear security. That’s really an embarrassment.”