FILE - Police officers stand watch as Boston Marathon runners race along the course, April 20, 2015, in Boston. The Boston Marathon returns to the traditional Patriots Day holiday, Monday, April 18, 2022, for the first time in three years, and runners and spectators should be prepared to encounter heavy security said Boston Police Superintendent Chief Gregory Long, during a news conference, Tuesday, April 12. (AP Photo/Robert F. Bukaty, File)

BOSTON (AP) — The Boston Marathon returns to the Patriots Day holiday next week for the first time in three years and runners and spectators should be prepared for heavy security, the city’s top law enforcement officer said Tuesday.

In addition to highly visible uniformed officers, plainclothes officers will be dispersed throughout the crowds, Superintendent in Chief and acting Commissioner Gregory Long said at a City Hall news conference.

There is no known credible threat to the race, he said. It’s been nine years since two bombs exploded at the finish line, killing three and injuring more than 260.

“The Boston Police Department has developed a robust and comprehensive security plan in an effort to provide safety to the runners, the spectators and all the visitors that come into the city of Boston,” he said.

Monday’s 126th Boston Marathon is the first to be held on Patriots Day since 2019, but comes about six months after the 2021 race, which was postponed until October because of the coronavirus pandemic.

“It’s unprecedented to hold two Boston Marathons in just six months,” said Boston Athletic Association Chief Executive Officer Thomas Grilk.

About 30,000 runners are expected to participate, he said, pumping about $200 million into the area’s economy.

Mayor Michelle Wu said “The marathon has always been about community, coming together, showing up, persevering, pushing forward no matter what may come our way, in the face of hate and division, fear or violence.”

Wu also noted that 2022 is the 50th anniversary of the first time women were officially allowed to enter, although women had run without registering prior to 1972.

The news conference was briefly interrupted by protesters opposed to Wu’s city worker vaccine mandate, who blew whistles and shouted “Shame on Wu.”

In addition to the heavy police presence, cameras are being set up along the route and observation points will be set up near the finish line area to monitor the crowds, Long said.

Bags will be subject to search, he said.

He called on the public to remain vigilant. “If you see something, no matter how small, something that seems not right or something out of the ordinary,” call 911 or find a nearby officer, he said.

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