The full list of the 18 new MPs for the province is not expected to be known until late on Friday night.
Counting in most constituencies began at lunchtime on Friday, a day after the rest of the UK.
This is because both the Westminster and local government elections were held simultaneously.
In 1997, the turnout was was 67%, but early indications this time suggest it was up to about 72% or 73%.
" Both the SDLP and Sinn Fein say they are going to win in West Tyrone so it will be a real nail biting finish "
Stephen Grimason BBC NI political editor
BBC Northern Ireland political editor Stephen Grimason said there were two specific battles being fought in the Westminster election in the province.
"The battle within unionism between the Democratic Unionist Party and the Ulster Unionists can be seen in places like east Londonderry, North Belfast, Strangford and North Down where the Ulster Unionist candidate, Lady Sylvia Hermon, is trying to take the seat from UK Unionist Bob McCartney," he said.
"Within nationalism the big battle is in West Tyrone.
"Both parties, the SDLP and Sinn Fein are both saying they are going to win it and both seem quietly confident so that will be a real nail biting finish."
Many regard the election in the province as a re-run of the referendum on the Good Friday Agreement in 1998.
The anti-Agreement DUP are set to focus on votes for the pro and anti-Agreement parties with a view to a possible re-negotiation of the historic peace Agreement.
'Higher turnout than usual'
"The DUP will regard this as a re-run of the referendum and they will be counting up all the yes and no votes," said Stephen Grimason.
"They say that if they get a big enough vote they could try to re-negotiate the Agreement, but all the other three main parties say no matter what happens there will be re-negotiation.
The number of voters was reported to be higher than usual in the North Down and West Tyrone constituencies.
More than 1,000,000 people were eligible to vote in Northern Ireland, in what was the fifth time the province had gone to the polls in five years.
A total of 100 candidates, including one who is standing in all four Belfast constituencies, contested 18 seats in the general election.
In the council elections, 982 hopefuls were in the running for 582 local council seats.
The counting of the council poll will not start until Monday 11 June, and will not be completed until the following day.