BOISE, Idaho (AP) — Idaho transportation officials say bridge inspectors found two undetonated explosive devices underwater at the base of a bridge that spans the Snake River near Nampa. Both devices were removed and destroyed by military experts, and a sweep of the area did not turn up any additional explosives.

It wasn't immediately clear how the explosives got there or how long they had been there.

Idaho Department of Transportation spokesman Jake Melder said the unexploded military ordnance was found underwater on the river floor near two of the piers supporting the bridge. A video of one of the devices posted by the Idaho Transportation Department online shows what appears to be a corroded artillery shell about 28 inches (72 centimeters) long that has some plant life growing either on or around it.

ITD worked with a bomb squad from the Nampa Police Department, the Mountain Home Air Force Base, the U.S. Air Force, the U.S. Navy and local law enforcement to safely remove the ordinances and determine next steps.

Melder said it was the first time that an explosive device has been found near an Idaho bridge, and the department believes the likelihood of it happening again is small. He referred questions about the nature of the device to the Mountain Home Air Force base; officials there did not immediately respond to questions from The Associated Press.

The Idaho Transportation Department routinely inspects bridges, but those inspections don't typically include an underwater inspection team. In this case, Melder said, the team was called in because the department was preparing to make repairs to the bridge supports as well as to the deck of the structure.

The divers found the first explosive on Oct. 31 and the next one the following day.

"The ordnances themselves were both located about 20 feet (6 meters) underwater," Melder said. "What the assessment showed where they were placed didn't show an immediate safety risk to the public. We didn't need to have cause for an alarm."

An Explosive Ordnance Device Dive Team was brought in from the Navy. The divers removed the explosives on Nov. 9, and the bridge was closed for about 20 minutes during that process, Melder said.

The bridge is on Highway 45 just south of Nampa. About 1,700 vehicles travel across it every day, according to the Idaho Transportation Department.

The last underwater inspection of the bridge was done in August 2016. No ordinance was seen during that inspection, though it's possible they were under silt or otherwise indistinguishable from rocks and other materials at the time.