Scotland's First Minister has written to the UK Government's transport secretary urging him to assure families of the victims of the Clutha helicopter tragedy that a report into the crash be published as soon as possible.

Nicola Sturgeon told Patrick McLoughlin that relatives of the 10 people who died when a police helicopter crashed on to the roof of the Glasgow pub on November 29 2013 were still waiting for answers.

An initial report from investigators said the aircraft suffered engine failure but the final conclusions of the Air Accidents Investigation Branch (AAIB) are yet to be published.

It said in November last year that the final report was expected to be published "in the middle of 2015".

In the letter, sent yesterday, Ms Sturgeon said: "While I fully understand the need for the most rigorous possible investigation, taking account of all possible factors, I am concerned at this apparent slippage in timescale.

"The Clutha families have already waited for almost two years, and I believe they should have an assurance that the report is now nearing completion and will be published imminently and certainly before the second anniversary of the tragedy.

"I would be grateful if you could give urgent consideration to this matter and take any necessary steps to expedite the publication of the final AAIB report.

The First Minister has previously raised concerns about the speed of the investigation in a letter to the Prime Minister.

An AAIB spokesman said: "The Clutha investigation continues to ensure the AAIB is satisfied all evidence and any additional information has been fully considered.

"The report is now being reviewed and will be published in due course."