Police Scotland said a 58-year-old man had been arrested at 0645 GMT and questioned by detectives before being released pending further investigation more than 11 hours later.

Its officers also carried out searches at a number of addresses linked to the investigation.

Peter Murrell, 58, who stood down as the SNP's chief executive last month, was taken into police custody on Wednesday morning, according to a party official who asked not to be named.

A marked police van was parked outside the couple's home in Glasgow, which was sealed off with blue and white police tape. A blue tent was also put up outside.

"A 58-year-old man who was arrested as a suspect earlier today ... has been released without charge pending further investigation," the force said in a statement.

A spokesperson for Sturgeon said it would not be appropriate to comment on a live police investigation.

"Nicola Sturgeon had no prior knowledge of Police Scotland's action or intentions. Ms Sturgeon will fully cooperate with Police Scotland if required however at this time no such request has been made," the spokesperson said.

The police investigation is looking at what happened to more than 600,000 pounds ($750,000) raised by Scottish independence campaigners in 2017, which was supposed to have been ring-fenced but may have been used for other purposes.

The party's accounts published by the Electoral Commission, the independent watchdog, showed that at the end of 2018 the party had about 411,000 pounds in cash or cash equivalents.

The SNP said it would not be appropriate to comment on any active police investigation but it has been cooperating with it.

'DIFFICULT DAY'

The arrest comes after a bruising few months for the SNP, which has dominated Scottish politics for most of the last two decades.

Humza Yousaf won a contest just over a week ago to replace Sturgeon as SNP leader and Scotland's First Minister that exposed deep divisions within the party, and he is now battling to restore the party's credibility.

Talking to reporters after news broke, Yousaf called the arrest a "difficult day for the party" and said that he wanted to reassure SNP members on the issues of transparency and party finances.

"The news this morning, it's challenging and it's difficult," he said.

Murrell, who had run the SNP for more than two decades and has been married to Sturgeon since 2010, resigned last month after accepting the blame for misleading the public about a plunge in the number of party members.

Sturgeon also stood down as the leader of Scotland's semi-autonomous government last month after eight years in power, saying she had become too divisive to lead the nation to independence from the United Kingdom.

In a referendum in 2014, Scots rejected ending the more-than 300-year-old union with England by 55% to 45%.

Britain’s vote to leave the European Union two years later when a majority of Scots wanted to stay, and Scotland’s handling of the coronavirus pandemic, brought new support for independence. However, the Conservative government in Westminster refuses to permit a new referendum.

Polls show support for the SNP and Scottish independence has dropped since Sturgeon's departure.

Police Scotland said a report would be sent to the Crown Office and Procurator Fiscal Service, Scotland’s prosecutors.