In last year's horror crash, which was found to be caused by human error, Vicky Balch, 21, lost her right leg.
An Alton Towers spokeswoman said: "On Thursday September 1, Alton Towers Resort stopped The Smiler to investigate claims a piece of debris that had fallen from a carriage.
"At no time were guests on the ride at any risk and all were safely removed from the ride promptly by staff in line with our comprehensive standard procedures.
"As the health and safety of our guests is our priority, the ride will remain closed whilst the Resort's technical team investigate the matter."