In the wake of the Boston Marathon bombings, Philadelphia has been retooling its security strategy for its marquee foot race, the Broad Street Run.

Before outlying the city's plan, Mayor Michael Nutter gave this preface: "Let me be very clear: there is no specific threat to the city of Philadelphia."

Nutter did announce some key changes. Runners will not be allowed to bring their own backpacks. If they want to check gear, the city will provide them with transparent equipment bags before the race begins.

Spectators will be prohibited from bringing bags and coolers into the Navy Yard area beyond the finish line and will be discouraged to carry backpacks at any stretch of the race.

"You will see an enhanced police presence," said Nutter about the tighter security. "You will see other things that are quite visible to you. There will be a bunch of other things that we're doing that you won't see, you shouldn't see and we're not going to tell you, for all the right reasons."

On Tuesday the city announced it would utilize three "SENTRY" mobile surveilance units during the race. These are essentially cameras mounted high on poles that can remotely pan, tilt, zoom with the ability to record day and night.

Sunday's race covers a 10 mile stretch of Broad Street, starting in Olney and ending at the Navy Yard in South Philadelphia.

Officials urge all planning to attend the event to register for emergency text message alerts at www.readynotifypa.org

In case of emergency the city will have three evacuation shelters in place: Benjamin Franklin High School (Broad and Spring Garden), High School for the Creative and Performing Arts (CAPA, Broad and Christian), and South Philadelphia High School (Broad and Snyder).

Race organizers expect the event will draw over 100,000 people including both runners and spectators.

Runners have been encouraged to wear red socks to show support for the victims in Boston.