The US Department of Energy’s nuclear security team will conduct helicopter flights over the Boston Marathon route ahead of Monday’s big race to test naturally occurring radiation levels.

Shelley Laver, a spokeswoman for National Nuclear Security Administration, said the tests are conducted to establish natural background levels before large events across the country.

“Every part of the country has different background radiation,’’ Laver said. “It also identifies the areas where it has a little elevation above.

“When we sit down and work with our data, it may show that there’s a hospital there that shows a spike because of a cancer treatment facility or equipment there.’’

A twin-engine Bell 412 helicopter will fly over the route from Hopkinton to Boston April 12 to 15 to measure naturally occurring radiation levels. The security agency said it routinely notifies the public of upcoming flights so that citizens who see the low-flying aircraft are not alarmed.

The agency has conducted the flights over the Marathon route since 2014.

Laney Ruckstuhl can be reached at laney.ruckstuhl@globe.com. Follow her on Twitter @laneyruckstuhl.