Further tests are to be carried out to determine the cause of Charles Kennedy's death.
The former Liberal Democrat leader died suddenly at his home in Fort William on Monday.
Police Scotland said there were no suspicious circumstances and that a post-mortem examination would be carried out but it has now been reported that further tests are needed.
A spokeswoman for Police Scotland told the Daily Record:
We can confirm that further tests are being carried out to establish the cause of death.
It remains a sudden and non-suspicious death and the Procurator Fiscal will be sent a report.
Labour's Tom Watson directed part of his touching tribute to the son of ex-Liberal Democrat MP Charles Kennedy, who was sitting in the House of Commons gallery.
Mr Watson directed part of his short tribute to ten-year-old Donald, saying: "Your father was a very great man. He stood up for what he believed in."
Former Lib Dem leader Nick Clegg called Charles Kennedy a "fully signed up member of the human race" in a touching tribute to his former colleague.
Mr Clegg, who was speaking in the House of Commons, also said that Mr Kennedy was the "polar opposite of a cardboard cut-out, points-scoring party politician."
The Prime Minister has paid tribute to former Liberal Democrat leader Charles Kennedy, saying "at his best, he was the best that politics can be."
MPs have paid tribute in the House of Commons to former Lib Dem leader Charles Kennedy, who was found dead at his home earlier this week.Read the full story ›
MPs will pay tribute to Charles Kennedy in the Commons today, after the former Liberal Democrat leader's sudden death aged 55.
His death is not being treated as suspicious, although the circumstances are still unclear.
Politicians will gather for a special Commons session at 12.30pm once the first Prime Minister's Questions of the new Parliament has finished.
Commons Speaker John Bercow said the session would help people "say what they think and feel and remember about our departed colleague, Charles Kennedy".
The broadcaster and journalist said he had a 'shared enemy' with the former Lib Dem leader as they bonded over their battle with alcohol.Read the full story ›
Politicians from across the political divide have paid tribute to Charles Kennedy after his sudden death at the age of 55.
Past and present Lib Dem leaders and the Prime Minister paid tribute to his 'character, wit and accomplishments' and said he will be remembered for his views against the Iraq War and the coalition.
Labour's Assembly Member Jenny Rathbone was heavily criticised for a message posted shortly after Charles Kennedy's death was announced.Read the full story ›
Sir Menzies Campbell has warmly remembered the former Liberal Democrat leader as a "gregarious" man who "enjoyed a good gossip".
Speaking to ITV News, Campbell spoke how in 2003 Kennedy made a huge impact in politics when he steadfastly denounced the march to war against Iraq.
Not long after the invasion, Kennedy and Campbell met the-then US President George Bush who was in the UK on a state visit.
"We went into the room in Buckingham Palace expecting their might be a bit of trouble," Campbell recalled.