AEC spokesman Phil Diak said about 140 of the 150 seats in the House of Representatives had been determined, while 10 seats were close on preferences - particularly the Western Australian electorate of Hasluck, Brisbane in Queensland and Corangamite in Victoria.
"On the ground we would say there is enough uncounted votes that they are not certain," he told ABC Radio on Friday.
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"Of course, if trends continue the same way, the parties in the lead, Labor in Corangamite, Liberals in Brisbane and also in Hasluck would win those seats."
In Brisbane, the most closely contested electorate, Mr Diak said about 80 per cent of the vote had been counted, however there were "easily" 12,000 or more votes such as absentee, postal and provisional ballot papers yet to be analysed there.
Provisional votes are granted when a person doesn't appear on the electoral roll, and are given the opportunity to vote anyway, so long as they provide positive identification that matches up with official electoral records.
The deadline for showing the AEC identification is late Friday afternoon, or the vote is forfeited.
Mr Diak said 1500 provisional votes were lodged in Hasluck, 1300 in Brisbane and 1200 in Corangamite.
"From an AEC point of view, we can't declare seats until they are absolutely beyond doubt," he said.
"It's not until the outstanding number of uncounted votes is smaller than the lead (candidate)."
Mr Diak said the AEC was ready to run a second election at any time, if need be.
