FRAMINGHAM — More than 3,500 police officers from at least 10 agencies, twice as many officers as last year, will line the Boston Marathon route next month as part of an intensive security operation that will employ more surveillance cameras, bomb-sniffing dogs, and limitations on spectators’ interactions with runners than ever before.
With at least 1 million people expected along the route, twice the number of spectators as in the past, police are discouraging spectators from wearing backpacks, hauling coolers, or carrying containers that hold more than a liter of liquid, state officials announced Monday.
“In this world, you never eliminate risk; you never bring it down to zero,” State Police Colonel Timothy Alben said in the bunker of the Massachusetts Emergency Management Agency Monday while flanked by officers from the eight cities and towns included in the Marathon route. “But we are working very hard at reducing the risk.”
FBI Assistant Special Agent in Charge Kiernan Ramsey said his agency has no indication that there will be another attack at this year’s race.
“At this time, we have no special intelligence that there is a threat,” Ramsey said.
Law enforcement anticipated no threat before last year’s bombings on Boylston Street that killed three and injured more than 260 people. In the days following the bombings, Boston police learned that one of the suspects, Tamerlan Tsarnaev, had been on a government watchlist, creating tension between local authorities and the FBI.
Ramsey said Monday that the level of information sharing between the FBI and local police departments is “second to none.”
“There is constant communication,” Ramsey said. “We have to get this right 110 percent of the time. Sadly, the bad guys only have to get it right once.”
Police said they will rely heavily on spectators to act as a second set of eyes on the streets and report anything that seems suspicious.
Unlike runners, who are forbidden from running with anything bulkier than fanny packs or fuel belts that carry water and snacks and are restricted from taking bags with them to the starting line in Hopkinton, spectators are not prohibited from bringing certain objects.
But state officials said they are strongly discouraging spectators from bringing the following items: backpacks; suitcases and rolling bags; coolers; glass containers or cans; any container capable of carrying more than 1 liter of liquid; handbags, packages, or bulky items more than 12 inches wide and 12 inches long; large blankets or comforters, duvets, sleeping bags; and any costumes that cover the face or bulky clothes.
Officials said they are discouraging those items because they could be used to conceal weapons.
To avoid being searched, spectators should bring their belongings in clear, plastic bags, officials said.
Boston police have already said they plan to stop anyone with a backpack or heavy bag along the part of the route that traverses the city, beginning at Audubon Circle and ending on Boylston Street in front of the Boston Public Library.
Police Commissioner William Evans, speaking to a group of Back Bay business owners, last week, said it makes no sense to prohibit spectators from bringing large bags to the race. If police turn away people carrying such items, the bags could be abandoned on the street or in an alley, which could create panic and divert officers, Evans said.
Boston police do not plan to use metal-detection wands or force spectators to file through security lines, he said.
The plan is to have a more laid-back approach, setting up metal barriers at intersections along Boylston Street near the finish line but allowing people to pass unless that area gets too congested.
People who carry their items in clear bags or carry nothing at all are unlikely to be searched, Evans has said.
In all, the marathon route goes through eight cities and towns. It is unclear what security checkpoints will look like on other parts of the route. Officials declined to say how many there will be.
Spectators will see more barriers separating them from the runners, from ropes to metal gates, and police have said they plan to flood the route with uniformed and plainclothes officers.
Bomb-sniffing dogs will patrol towns such as Brookline, where the canines have not been used in the past.
Kurt Schwartz, director of MEMA, said that in the smaller towns where the route winds through neighborhoods, people can still bring coolers out to their front lawns and watch the runners as they always have.
The goal, Schwartz said, is to keep the Marathon a “fun, festive, family-oriented day.”
To that end, police officers will also be told to be reasonable, officials said.
Local officers have been trained to watch for strange people acting furtively, officials said, not bother neighbors they are used to seeing every year on their front stoop, watching the race and drinking soda from a cooler.
“We are urging common sense,” Schwartz said.
The cost of beefing up security has not yet been tallied, he said. Typically, costs for state resources alone, such as State Police and fire services, are several hundred thousand dollars, Schwartz said.
“I can tell you that the state costs [this year] are much greater than that,” Schwartz said.
Follow her on Twitter @GlobeMCramer.