The Kensington count has been suspended, meaning the constituency won't yet be electing its MP.
Work at the count has been delayed – with a result not expected until at least tonight, and perhaps tomorrow.
Reports earlier in the night had suggested that Labour would take the seat from Conservatives. But the results appear to have been so close that repeated recounts are necessary – and the staff are not available to complete the count.
Tellers are now reportedly too tired to take part after having spent almost 12 hours counting votes. They had been seen falling asleep at their tables as they waited for counts and recounts to finish.
Now those staff will be given a chance to "rest and recuperate" before heading back to count all over again.
Election officials had already been forced to conduct two recounts, according to people on the ground. They didn't finish with a decisive result – with some reports suggesting there may be dozens of votes in it – and so another count will have to happen.
In a statement, returning officer Tony Redpath said: "The provisional result of the election was known at approximately 2am. That result was very close and a recount was therefore requested.
"The result on that recount also remained very close.
"A request for a third count was therefore made. At this stage staff had been up all night and were becoming visibly tired. In order to have confidence in its accuracy, the recount has been suspended to allow staff to rest and recuperate.
"The count will recommence as soon as possible and details will be posted on our website and on social media."
Kensington has been a strongly Tory seat since its inception. But it also staunchly voted to remain in the Brexit referendum, leading Labour to contest the seat actively during the election campaign.
The seat is one of only four seats left to declare. The rest are all neighbouring seats in the South West: Cornwall North, Cornwall South East and St Austell & Newquay, all of which are expected to stay with the Conservatives.
