Boston Marathon Security: Undercover Cops Key

Officials said undercover police officers are integral to the security plan for this month's Boston Marathon.

WHDH-7News reported a larger-than-usual crowd is expected after last year's bombings near the finish line, which killed three people and injured more than 250.

Boston Mayor Marty Walsh and Police Commissioner William Evans on Saturday said there will be a huge law enforcement presence along the marathon route this year. The marathon will be held Mon., April 21.

"You're going to see some uniform presence out there and we're going to really increase the undercover officers working in and among the crowd at Copley and along the route," Evans said, according to WHDH.

Other security measures include:

• Backpacks will not be allowed. Runners will be given clear plastic bags for their personal items
• Unregistered "bandit" runners who have historically participated in the race will be prohibited this year
• There will be security checkpoints throughout the race area
  
• The size of water bottles will be limited
• Costumes with facial coverings will not be allowed