A low-flying helicopter will reportedly make several passes over the Boston Marathon route this week to measure naturally occurring radiation.

The survey is at the request of marathon organizers and state and local officials, according to the State House News, and is meant to compare changes in radiation levels and detect radiological threats. 

"That data that we collect is provided to said parties and gives them a baseline of what the situation looks like today," Shelley Laver, deputy director of public affairs for the NNSA, told the News Service.

Between Tuesday and Friday, the National Nuclear Security Administration will use the twin-engine Bell 412 helicopter to make a grid pattern above the 26.2 mile route at about 150 feet above the ground at speeds of about 80 miles per hour, the agency said. Officials want residents to be aware of the survey so they do not become alarmed, CBS reported.

Related: No credible threats to 2016 Boston Marathon

The NNSA has conducted a radiation survey in the Boston area before the Boston Marathon each of the last two years. Three years ago, terrorists detonated two pressure cooker bombs near the marathon finish line, killing three and injuring more than 260 spectators.

According to the United States Government Accountability Office, the surveys can also be used to "measure contamination levels after a radiological attack to assist in and reduce the costs of cleanup efforts."

"If something were to occur, they would have that, and if there was suspicion of some sort of a use of nuclear or radiological source in any kind of event, federal, state and local teams would come in and assess and be able to do a comparison to the baseline," Laver said.

Additional reporting by the State House News Service.