Mexico’s public-health scare turned into a logistical hurdle Thursday as authorities sought to safely put a stolen load of radioactive material back into its container.

As officials worked on the material, federal police and soldiers formed a cordon of several hundred yards around the field in Hueypoxtla where a container of highly radioactive cobalt-60 was abandoned after it was stolen from truck drivers transporting it to a storage facility in central Mexico.

UPDATE: Police block access to Mexican hospital; 6 reported to have been admitted with radiation exposure

The International Atomic Energy Agency (IAEA) said the “extremely dangerous” cargo of pellets used in hospital radiotherapy machines had been removed from its protective casing, but “there is no indication that it has been damaged or broken up” and there is “no sign of contamination to the area.”

Mexican authorities estimated it could take a couple of days to safely contain and remove the cobalt-60 and that it does not pose a health risk to the public.

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“At this moment the situation is not that serious, because the source has been located and it’s being protected,” said Benjamin Ruiz Loyola, a chemistry professor and hazardous substance expert at the National Autonomous University of Mexico.

The theft of the material sparked international concern because of the possibility that the cobalt-60 could be used in a “dirty bomb.” But by Wednesday afternoon, authorities had found the stolen Volkswagen cargo truck and the radioactive material.

President Obama’s national security team monitored the situation in Mexico “very closely” Wednesday, and there is no reason to believe the stolen truck posed a threat to the United States, White House press secretary Jay Carney said.

“What's most important is that the vehicle and equipment were recovered and the situation was resolved,” Carney said.

The drivers of the cargo truck were sleeping at a gas station this week when gunmen assaulted them and stole their truck. Mexican nuclear safety officials said they believed the carjackers did not know what they were stealing and that they may die from exposure to the radioactive material.

The IAEA said in its statement that it “would probably be fatal to be close to this amount of unshielded radioactive material for a period in the range of a few minutes to an hour.” It is unclear how long the material was handled by the carjackers or others who found it later.

Mexican officials said members of one family who came across the container were checked for contamination but appeared to be fine.