Former Scottish first minister, Nicola Sturgeon, claimed to be innocent after she was arrested as part of an investigation into the finances of the country's ruling party.
Detectives quizzed Sturgeon for around seven hours as part of the "Operation Branchform" investigation into the finances of the Scottish National Party (SNP), Scotland's dominant political force.
She was later released pending further investigation, said Police Scotland.
"To find myself in the situation I did today when I am certain I have committed no offense is both a shock and deeply distressing," Sturgeon wrote in a statement issued on Twitter after her release.
"I would never do anything to harm either the SNP or the country," she added.
Given the ongoing investigation, there was a limit to what she could say, she said.
But she insisted: "Innocence is not just a presumption I am entitled to in law. I know beyond doubt that I am in fact innocent of any wrongdoing."
A statement earlier Sunday from Police Scotland said: "A 52-year-old woman who was arrested earlier today as a suspect in connection with the ongoing investigation into the funding and finances of the Scottish National Party, has been released without charge."
Her arrest is the third in the probe that has sent shockwaves through Scotland's politics.
The brewing scandal has plunged the SNP into a deep crisis and damaged its dream of an independent Scotland.
Labour's shadow Scottish secretary Ian Murray reacted to the latest news by saying: "For too long, a culture of secrecy and cover-up has been allowed to fester at the heart of the SNP."
Meanwhile, Scottish Lib Dem leader Alex Cole-Hamilton said: "It's fair to say that today's events will have huge ramifications both for the SNP and the future of Scottish politics."
Sturgeon's husband Peter Murrell, the former chief executive of the SNP, was arrested in April as part of the probe.
At the time, police raided the Glasgow home shared by the couple, erecting a crime-scene tent in the front garden, and SNP headquarters in Edinburgh.
Murrell has long faced questions over the alleged diversion of 600,000 pounds ($750,000) in SNP donations that were meant to support its drive for Scottish independence.
He also failed to declare a personal loan to the party of more than 100,000 pounds.
Party Treasurer Colin Beattie was also arrested in April.
Sturgeon made her final appearance as First Minister in the Scottish Parliament in March.
After more than eight years at the helm, Sturgeon said in February that she lacked the "energy" to carry on and was stepping down.
But the police investigation into Murrell, whom she married in 2010, had been a cloud over her head.
Murrell resigned from his SNP leadership post in March after the party falsely denied to the media that it had lost 30,000 members.
The disclosure came as the SNP held a bitter election to replace Sturgeon as party leader and Scotland's first minister, eventually won by Humza Yousaf.
Yousaf denied that Sturgeon had quit knowing the police investigation was about to come perilously close to home.
"Nicola's legacy stands on its own," he said.
Following Murrell's arrest, Yousaf said "clearly it's not great, and I think the sooner we can get to a conclusion in this police investigation, the better.
"I've never been an office bearer in the party, I've not had a role in the party finances," he added.
Recent surveys show only around 45% of Scots back their nation leaving the U.K. – the same minority recorded in a 2014 referendum, which London insists settled the matter for a generation.
