The United States took precautionary steps along its border with Mexico on Wednesday after thieves stole a shipment of highly radioactive material, the White House said.

President Obama was briefed by chief counterterrorism aide Lisa Monaco Wednesday morning and received updates throughout the day, White House press secretary Jay Carney said on Thursday.

"Our national security team monitored that situation involving the stolen vehicle and medical equipment very closely yesterday," Carney said. "Throughout the day, we were in close touch with Mexican officials."

The highly radioactive material was found Wednesday afternoon, two days after the truck that carried it was stolen. The cobalt-60 had been removed from its protective container, likely dooming anyone who opened the box to death by radiation poisoning within days.

Carney did not elaborate on what security steps were taken on the U.S.-Mexico border but said that the White House had no "reason to believe that the stolen vehicle ever posed a threat to the United States.

He added that the U.S. was "pleased that the vehicle and equipment were recovered and that the situation was resolved."

The material had come from medical equipment at a hospital in Tijuana and was to be deposited at a nuclear waste facility outside of Mexico City. Authorities there say it could take up to 48 hours to resecure the material and transport it to a waste site, according to The Associated Press.