Officials and law enforcement spoke about safety and security precautions for this year's Boston Marathon on Wednesday morning.
More than 5,000 uniformed and plainclothed officers will be along the race route, and there could be some bag inspections and security checkpoints.
Runners and spectators are being asked not to bring backpacks, bulky items, coolers, glass bottles or containers capable of carrying more than 1 liter of liquid, large sticks, signs or poles with them to the race. In addition, anyone bringing extra clothing or possessions is being asked to carry them in clear plastic bags.
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Drones are also not going to be allowed, other than two tethered drones that public safety officials are using at the starting line in Hopkinton to keep a close eye on the crowds. Up to 1 million spectators are expected to line the course.
They'll also use large public works vehicles to block access to key pedestrian areas. That's a response to recent attacks in France and Germany, where trucks were used to mow down people packing sidewalks.
Spectators also shouldn't plan to meet runners at the finish line, but should make other plans for convenience and safety.
Most importantly, officials are asking runners and spectators to be on the lookout for anything suspicious.
"Be aware of your surroundings, be vigilant," said Kurt Schwartz, director of the Massachusetts Emergency Management Agency. "If you see something that doesn't feel right, report it to the nearest public safety officer or call 911."
Harold Shaw, special agent in charge of the FBI's Boston Division, noted that this year marks the fourth Boston Marathon since the 2013 bombings that killed three spectators and wounded more than 260 others.
"All participating in this event should feel comforted by the professionalism and thoroughness expended by everyone involved in this year's event," he said. "Yet we must remain guarded."
Shaw said the FBI is unaware of any specific threats related to this year's marathon at this time. But there is some concern over the potential for lone wolf, homegrown extremists.
This year's Boston Marathon will take place on April 17.