Part of the Upper Newtownards Road has been closed between the Knock traffic lights and Cabin Hill Park on Sunday afternoon.
A number of homes have been evacuated, with Stormont Presbyterian Church made available for those affected.
Police area the scene and diversions are in place.
Police are currently attending a security alert at Upper Newtownards Rd in East Belfast. Part of the road is closed, diversions are in place
More top news
Six were wounded, two seriously, after an ultra-Orthodox man stabbed several people at Jerusalem's annual Gay Pride march.
Video shows inside the bin lorry in the immediate aftermath of the Glasgow city centre crash that killed six people days before Christmas.
A woman who underwent a keyhole hysterectomy woke up to find two of her teeth had gone missing.