A car, hijacked earlier in the city, was abandoned in a car park outside the Templemore Leisure centre.
Dissident republicans were blamed for disrupting the Foyle and East Londonderry counts.
Police across Northern Ireland had been on high alert because of the security threat and were expecting some sort of act by republicans opposed to the peace process.
As well as election staff and the counters for the two constituencies, supporters of the various candidates also had to be evacuated.
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