Police were called to the Lowry Outlet on Salford Quays after man clambered onto a car park roof.
The Quays, outside the shopping centre, was shut in both directions while police spoke to the man.
Transport for Greater Manchester tweeted: "Due to a Police incident, The Quays (outside the Lowry Outlet) is currently closed in both directions. As a result, MCRMetrolink replacement bus services are being diverted along Broadway and Trafford Road. Media City and Harbour City stops will not be served."
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There are reports of heavy traffic between Capital Quay and Broadway.
