BOSTON (CBS) – Starting Thursday, don’t be surprised to see a low-flying helicopter along the Boston Marathon route.

Breaking News From WBZ Boston

The Department of Energy’s National Nuclear Security Administration will be conducting radiation tests between Hopkinton and Boston using low-altitude helicopter flights. The tests are expected to go through Sunday.

Radiation-detecting helicopter operated by NNSA (WBZ-TV)

The department says monitoring naturally occurring radiation levels is a normal part of preparing for any major public event.

These flights have been taking place before the marathon since 2014, and citizens shouldn’t be alarmed by the low-flying aircraft. The helicopters will be flying in a grid pattern at about 150 feet above the ground and going about 80 mph.

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