Students at Kingston University London needed to go away a part of the Penryhn Road campus simultaneously as officers look into it.
The Met Police stated it turned into known as at 09:15 BST on Thursday and had asked for assistance from the Ministry of Defence.
A cordon in the region in Fassett Road closed two close by polling stations.
At approximately 20:30, police said approximately 1,500 homes had been evacuated as a precaution, with cordons anticipated to remain in location until Friday afternoon.
Commander Mark McEwan stated: “Rest centres and assistance are being provided via our partners. The operation is possible to keep at some stage in the nighttime.”
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At 11:30, Kingston University stated the campus could “be closed for the relaxation of the day.”
By the afternoon, the cordon has been prolonged to cover the Knights Park campuses, the University’s nursery, and some pupil halls.
Kingston Council showed two polling stations getting used for the European elections had been closed while the tool is dealt with.
St John, the Evangelist Church in Grove Lane, was moved to St Mark’s Church in Surbiton, and St Raphael’s Catholic Church Hall in Portsmouth Road was moved to Glenmore House, The Crescent.