Former SNP leader and First Minister Nicola Sturgeon was arrested in connection with the ongoing investigation into the funding and finances of the party.
Police confirmed a 52-year-old woman was taken into custody as a suspect and is being questioned by detectives.
This follows the arrest and release of her husband, ex-SNP chief executive Peter Murrell in April 2023.
A spokesperson for Ms Sturgeon said she was cooperating with the investigation.
He said: “Nicola Sturgeon has today, Sunday 11 June, by arrangement with Police Scotland, attended an interview where she was to be arrested and questioned in relation to Operation Branchform.
“Nicola has consistently said she would cooperate with the investigation if asked and continues to do so.”
A spokesperson for the SNP said:
“These issues are subject to a live police investigation.
“The SNP have been cooperating fully with this investigation and will continue to do so however it is not appropriate to publicly address any issues while that investigation is ongoing.”
On April 5, 2023, officers searched Ms Sturgeon’s home and the party’s headquarters in Edinburgh.
Mr Murrell was later released without charge.
A luxury motorhome was also seized by police from outside the home of Mr Murrell’s mother in Dunfermline.
Almost two weeks later, SNP treasurer Colin Beattie was arrested and released without charge.
Mr Murrell and Mr Beattie were both treated as suspects and were taken into custody for the legally defined period of up to 12 hours of questioning before being released pending further inquiries.
Under the Criminal Justice (Scotland) Act 2016, police can release a suspect for further investigation, but they can be re-arrested at a later date.
Nicola Sturgeon served as Scotland’s first minister for eight years.
Her shock resignation came on February 15 when she said she knew “in my head and in my heart” this was the right time to step down.
She is the longest-serving First Minister and was the first woman to hold the position.
Ms Sturgeon insisted her resignation was not in response to the “latest period of pressure”, which has included controversies over gender reforms, trans prisoners and the strategy on independence.
Humza Yousaf has since become First Minister.
But within a month of her last day on March 28, the investigation into the SNP’s finances – which began almost two years ago – came to light.
Complaints had been made relating to more than £600,000 that was donated to the SNP by activists.
The money was raised after the party sought to raise funds for a future referendum campaign, and Police Scotland launched Operation Branchform to examine what happened to it.