PHILADELPHIA (AP) -- A former Arizona State University professor is facing charges for allegedly claiming to have explosives at Philadelphia's iconic Liberty Bell.

Police say 41-year-old Carlos Balsas of Tempe, Ariz., entered the tourist site in Philadelphia's historic district around 11 a.m. Saturday.

An officer at an entrance security check told police that a man stated his two backpacks contained explosives.

The man left and security officers notified park rangers. Police cordoned off the street on Independence Mall where the Liberty Bell building is located.

Balsas was stopped by park rangers a block away and was arrested after a brief struggle. Two backpacks were found nearby but there were no explosives inside.

Balsas was charged Sunday with terroristic threats, bomb threats, possessing an instrument of crime, reckless endangerment and related offenses.