According to the San Antonio Police Department, two employees from the Department of Energy's Idaho National Laboratory stayed at the Marriott on Loop 410 and I-10 in March of 2017. The next morning, they found that their rental vehicle was broken into and two pelican cases carrying the radioactive materials were gone.

Inside one pelican case were six various kinds of meters, some used to survey radioactive materials. In the second case were two sample counters, one plutonium check source and one cesium check source which are used to calibrate radiation detectors.

"From the perspective of a nuclear weapon, this is not a concern. From the perspective of the radiation risks from plutonium, this is a concern," said Professor Alan Kuperman with UT-Austin.

Professor Kuperman noted that the amount of plutonium lost was likely just a few grams and you'd need about 1,000 times that to make a nuclear weapon, like the bomb dropped on Nagasaki in World War II.

But if plutonium becomes aerosolized, it can be even more dangerous.

"Health officials say if you do inhale a tiny speck of plutonium, it is guaranteed, eventually, to give you cancer," he said.

Professor Kuperman added that the cesium isotope that was also taken is highly radioactive and poses a much greater risk.

"From a dirty bomb standpoint, that is perceived as a greater threat. That could be used as a terrorist weapon in a liquid form, in an aerosolized form, and that is a much higher radiation level,” Professor Kuperman said.

Congressman Joaquin Castro requested more information from the U.S. Department of Energy Secretary Rick Perry.

In a letter to Perry, he said:

"I am deeply concerned with reports of the March 21, 2017 incident in San Antonio in which two Department of Energy employees lost radioactive material. Reports indicate the material unaccounted for (MUF) includes radioactive samples of plutonium and cesium posing serious U.S. national security and health risks to my district, Texas and our nation."

KENS 5 reached out to the Department of Energy and a representative replied, saying:

"INL officials immediately reported this incident to DOE, as well as state and federal law enforcement officials. Members of the public were not at risk at any time. Efforts to recover the devices are currently under the jurisdiction of law enforcement. Safety is the number one priority for the Department."

The Department of Energy also said that, if exposed, the dose from handling these devices is less radiation than we receive in a typical day from natural sources of radiation.

Professor Kuperman agrees that exposition isn't dangerous if they stay outside of the body. But if ingested in any way, that certainly would not be the case.

Police have no clues or evidence. If you have any information, police are requesting that you give them a call.