The Garda Siochana police force said eight people had been hospitalised and that it “can now confirm nine fatalities as a result of this incident”.
“The search and recovery for further fatalities continues” at the site in the village of Creeslough,” it said.
The cause of the explosion remained unknown and police had yet to announce the launch of an inquiry as the search through rubble went on.
The toll from Friday’s explosion had already risen from three to seven overnight.
Rescue efforts by Ireland‘s emergency services went on through the night after the blast ripped through a petrol station forecourt and a nearby apartment complex.
An aerial photograph taken after the explosion showed the petrol station building destroyed.
Two two-storey residential buildings behind had collapsed, while the facade of a similar adjacent building was blown off.
Resident Kieran Gallagher, whose house is about 150 metres (500 feet) from the scene, said the blast sounded like a “bomb”.
“I was in my house at the time and heard the explosion. Instantly I knew it was something — it was like a bomb going off,” he told the BBC.
At a service at the local church on Saturday morning, Father John Joe Duffy said the community had been hit by “a tsunami of grief”.
Many emergency services vehicles remained at the scene overnight, including fire services from both sides of the border with British-run Northern Ireland.
Gardai and civil defence were also involved, and a coastguard helicopter airlifted some of the injured from Letterkenny University Hospital to the capital Dublin.
‘Shocked and numbed’
The university hospital, some 15 miles (24 kilometres) from the explosion, was placed on an emergency footing to deal with “multiple injuries”, it said in a statement.
Ireland’s premier Micheal Martin called it a “very dark day” as he spoke to the media briefly before heading to the scene.
“The scale and enormity of it, it’s such a small community, it means that almost everybody will know on a friendly basis people who’ve lost their lives,” he said.
“It’s a very dark day for the people of Donegal and for Ireland.”
Martin earlier thanked members of the emergency services who were working non-stop “in extremely traumatic circumstances”.
Agriculture Minister Charlie McConalogue, who represents northeast Donegal in the Irish parliament, compared the scenes to events during the decades-long sectarian conflict on the island of Ireland over British rule in Northern Ireland.
“People are shocked and numbed,” McConalogue told Irish broadcaster RTE.
“The scenes from the event are reminiscent of the images from The Troubles years ago, in terms of the scene on the ground and the damage and the debris.”
Creeslough is around 30 miles (50 kilometres) from the border with Northern Ireland and has a population of about 400 people.
The Applegreen service station is on the N56 road, which loops around the northern tip of the Irish republic.
Applegreen tweeted that the news was “devastating”. “Our thoughts and prayers are with the families and friends of the deceased, those who have been injured, and the wider Creeslough community,” said the company.
Ireland’s President Michael D. Higgins expressed his “shock” in an official statement.
“This tragedy is a terrible blow to a community that is closely knit and where every loss and injury will be felt by every member of the community and far beyond,” he said.
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