(WBIR) More than 36,000 runners will take their marks at the start line for the 118th Boston Marathon today, the first since last year's attack, killing three people and injuring hundreds more.

When the bombs went off last year, many runners were still on the course. This year they've all been invited back to finish what they started.

The Red Cross announced Sunday that they'll have mental health volunteers stationed along the route to help anyone dealing with anxiety or stress.

Authorities have tightened security for this year's race. Among the regulations, runners won't be able to wear backpacks.

Police said they plan on having 3,500 officers on patrol, either in uniform or undercover. There will also be more than 100 security cameras, which are more high tech than those that caught the bombing suspects last year.

Officials also said they have 13 miles of steel barricades, at least 40 checkpoints, and nearly four times the number of bomb sniffing dogs to help keep people safe.

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