Many organizations are reviewing security measures in light of the Boston Marathon bombings, including this weekend's St. Jude Country Music Marathon in Nashville, Tennessee.
Federal and state officials say they have reviewed security plans for Saturday's marathon and half-marathon, which brings around 30,000 runners to Music City.
The U.S. Postal Service says all mailboxes along the route of the marathon will be blocked as a precautionary measure. Hundreds of law enforcement and security officers are expected to be along the route.
The FBI says there are no known security threats, but officers will be vigilant in the wake of last week's bombings.