In March 2017, thieves made off with radiation detectors and small disks of radioactive plutonium and cesium that were stashed in the back of a rental car, the Center for Public Integrity reported on Monday. The gear had belonged to two Idaho National Laboratory employees, who’d been sent to recover radioactive materials from a lab in Texas.

The employees’ tools for the mission? Radiation detectors and dime-sized disks of plutonium and cesium used to make sure the detectors were working properly. But the entire kit was stolen from their rental car when it was parked at a Marriott in San Antonio, Texas. The theft was immediately reported to law enforcement and the Department of Energy, and it didn’t put the public at risk, according to a DOE official. But the first time the public heard about it was on Monday thanks to the Center for Public Integrity.

To be clear, the theft of this particular radiological material isn’t that worrying by itself; the disks are sealed and contain less radioactivity than a smoke detector, according to a DOE official. But the entire fiasco reflects a bigger problem, the Center for Public Integrity says: the government isn’t keeping a close enough watch on radiological material that could be made into a bomb or radiological exposure device. For example, in 2009 the DOE’s inspector general found that 45 pounds of highly enriched uranium had gone missing, the Center for Public Integrity reports.

“It is more likely that they were taken to be sold for financial gain rather than to be used in a radiological weapon.”

The theft in San Antonio probably wasn’t targeting the radiological material specifically, says Grace Liu, a research associate who works at the James Martin Center for Nonproliferation Studies. “These materials may not have even been labeled as plutonium or cesium so they were taken because they looked expensive,” she says in an email to The Verge. “Either way, it is more likely that they were taken to be sold for financial gain rather than to be used in a radiological weapon.”

But the fact that the radiological materials could be stolen is a bad sign. “I do think that this is a systemic issue with the safety culture surrounding transport of sensitive items within the labs and the military,” Liu says. Miles Pomper, a senior fellow who also works at the James Martin Center for Nonproliferation Studies, is particularly concerned that the Department of Energy didn’t alert the public about the theft. “Even more importantly, the behavior of the officials and the lack of reporting and transparency is of great concern,” he says in an email to The Verge.

“We first need to challenge the assumption that just because they are in government hands they are safe.”

The Center for Public Integrity’s story references a report published by the Nuclear Threat Initiative (NTI), which Pomper worked on. The NTI report says that the lack of international standards for keeping military nuclear materials secure leaves major gaps in global security. The NTI has a few recommendations for how to close them, including boosting security of military materials, having an independent watchdog oversee security efforts, and increasing transparency about investigations into accidents and security breaches.

Liu adds that developing strict enforcement measures and establishing standards for transporting, storing, and recovering radiological materials will also be key. But when it comes to radiological materials, there’s an even more important step to take first, Pomper says: “We first need to challenge the assumption that just because they are in government hands they are safe.”