The race is on to become the first constituency in the country to declare.
Houghton and Sunderland South was the first constituency to declare its result in the 2010 and 2015 elections, although it was beaten by Newcastle Upon Tyne Central in 2017.
Labour won the seat in 2017 with 12,341 more votes than the Conservatives.
Labour won 24,665 votes last time, taking 59.5 per cent of the vote.
The Conservatives got 29.7 per cent of the vote, UKIP won 5.7 per cent, the Liberal Democrats won 2.2 per cent, the Green Party got 1.8 per cent and an independent candidate, Michael Watson, got 1.2 per cent.
All 121 ballot boxes in all Sunderland seats have arrived.
The result will be the first real test of whether the exit poll is right, and the extent to which Labour have lost support in the North of England to the Conservatives.
The town voted for Brexit by 61.3 per cent to 38.7 per cent, providing an early indication that the Brexit campaign had won.