Counting of Kenyan election results has all but stopped because of problems with the electronic systems.
Returning officers were ordered to physically deliver paper copies of their constituency's vote tallies to the counting centre in the capital.
Election officials have urged patience.
Uhuru Kenyatta leads in the presidential race. He faces trial at the International Criminal Court over claims - he denies - of being behind post-election violence in 2007-2008.
His closest rival is outgoing Prime Minister Raila Odinga, who with results in from over 40% of polling stations has 42% of the vote compared to Mr Kenyatta's 53%.
More than 1,000 people were killed in the violence which broke out in 2007-2008 after Mr Odinga claimed he had been cheated of victory by supporters of President Mwai Kibaki, who is stepping down after two terms in office.
Some electoral officials have had to drive hundreds of kilometres to the counting centre in Nairobi to deliver the paper copies of their returns.
The BBC's Solomon Mugera in Nairobi says various returning officers have been seen arriving during the early hours of Wednesday.
So far some 330,000 spoiled ballots have also been counted - well over double the number of votes cast for the third-placed candidate, Musailia Mudavadi, who trailed far behind with just over 148,000 votes, or 3%.
Some put this down to confusion, with voters having six ballots papers to complete, while some observers note that officials have tightened their rules on what constitutes a spoiled paper.Continue reading the main story