SETE, the body which runs the site, said bomb disposal experts as well as police were scouring the area, including a restaurant located on one of the floors.
“It’s a usual procedure in this kind of situation which however is rare,” a spokeswoman said.
Visitors were evacuated from both the three floors and the square under the monument shortly after 1:30 pm (1130 GMT).
Construction work on the tower began in January 1887 and was finished on March 31, 1889. It received two million visitors during the World’s Fair of 1889.