Former SNP chief executive Peter Murrell, the husband of Nicola Sturgeon, is understood to have been arrested by Police Scotland over an investigation into the party’s finances.
Detectives are said to have questioned him and searches have been carried out at a number of properties.
Mr Murrell, 58, stepped down as chief executive during the recent leadership campaign.
Police Scotland have been investigating the spending of money which was earmarked for Scottish independence campaigning.
Mr Murrell married Ms Sturgeon in 2010.
It said: “A 58-year-old man has today, Wednesday April 5, been arrested as a suspect in connection with the ongoing investigation into the funding and finances of the Scottish National Party.
“The man is in custody and is being questioned by Police Scotland detectives.
“Officers are also carrying out searches at a number of addresses as part of the investigation.
“A report will be sent to the Crown Office and Procurator Fiscal Service.
“The matter is active for the purposes of the Contempt of Court Act 1981 and the public are therefore advised to exercise caution if discussing it on social media.
“As the investigation is ongoing we are unable to comment further.”
The SNP released a statement saying: “Clearly it would not be appropriate to comment on any live police investigation but the SNP have been co-operating fully with this investigation and will continue to do so.
“At its meeting on Saturday, the governing body of the SNP, the NEC, agreed to a review of governance and transparency – that will be taken forward in the coming weeks.”