Store Street, near Piccadilly Station, has been cordoned off between London Road and Jutland Street.
Emergency services are on the scene.
People were urged to avoid the area.
Police said “unknown white powder” was delivered in an envelope to an office building, with an evacuation in place.
Greater Manchester Police said in a statement: ‘Shortly before 2:30 p.m. officers were called to report that an unknown white powder had been delivered in an envelope to Piccadilly Gate, Store Street, Manchester.
“The building was evacuated as a precaution and a cordon and road closures are currently in place. Please follow @OfficialTfGM for updates.
“Emergency services are present and inquiries are ongoing. “
Greater Manchester Police also tweeted about the incident from their Manchester city center account.
They tweeted: ‘We are currently facing an ongoing incident on Store Street in Manchester city center. Store Street is closed between London Road and Jutland Street, with a police cordon in place.
“Can you avoid the area while emergency services deal with this incident.” Sgt K. ”
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