The head of the investigation into the death of Sheku Bayoh in police custody will "listen to the concerns" his family have in a meeting this week.

Police Investigations and Review Commissioner (Pirc) Kate Frame will meet on Thursday relatives of Mr Bayoh, 31, who died after being restrained by officers in Kirkcaldy, Fife on May 3.

Ms Frame said she understands the need for answers around the death and wants to hear any additional information from his partner Collette Bell and family they think might be relevant to the investigation.

A post-mortem examination proved inconclusive and a Sunday newspaper reported family concerns that experts called in by investigators may blame a medical condition known as excited delirium, which has been cited in other custody deaths.

It is used to describe the state of a person who, as a result of mental illness or drug use, becomes agitated, violent and displays extreme strength.

The Pirc said the fact that forensic pathology experts from outside Scotland have been contacted is not a sign that it has focused its investigation on a particular cause of death and that all lines of inquiry are being explored to establish the circumstances.

Ms Frame said: "I fully empathise with the deceased's family and their need for answers in relation to the circumstances surrounding the death of Sheku Bayoh on May 3.

"I'm looking forward to meeting with the Bayoh family on Thursday and welcome the opportunity to discuss my role as commissioner and the investigation process.

"I will listen to the concerns that the family have raised recently and update them on the further work that is being undertaken before the matter is fully reported to the Lord Advocate.

"I'm also keen to receive any additional information from them which they consider might be relevant to the ongoing investigation.

"I fully recognise the family's need for a clear understanding of what caused Sheku Bayoh's death, and despite the fact that the post-mortem conducted shortly after his death was inconclusive, I remain committed to thoroughly investigating all lines of enquiry."

The family of Mr Bayoh, a trainee gas engineer and father-of-two, last week met the Lord Advocate Frank Mulholland to discuss the investigation.

Lawyer Aamer Anwar said: ''The Bayoh family have stated from day one that Sheku acted out of character and that if he broke the law then the police had a right to act, but he did not deserve to die.

''When officers armed with CS, pepper spray, batons and handcuffs and restraints, try to subdue someone by force and that person dies, the number one question is whether their actions resulted in that death.''

Police Scotland said they await the conclusion of the Pirc investigation and remain committed to co-operating fully with the body's inquiries.