"A cordon is in place in Piccadilly Gardens after reports of a suspicious package were made. A man aged 26 has been detained by police and enquiries into the incident are ongoing," the police said on its Twitter blog.
The police also called on the people working nearby to follow the directions from the police and stay indoors if asked to do so.
The man who was detained by the police earlier on Friday was officially arrested and put in custody, the police said in a separate tweet.
"Transport links including the Metrolink have been affected as a result of the cordon. As part of enquiries, Oldham Library has also been evacuated after reports of a suspicious device found there," the police stated.
Updates are to follow, the police added.
Earlier, photos shared via social networks showed an area at Piccadilly Gardens sealed off with police tape while law enforcers are standing guard around the area.