A new mother was found dead at a Scottish hospital hours after going missing.

Amanda Cox, 34, from Peebles, in the Scottish Borders region, did not return to the maternity ward at Edinburgh Royal Infirmary on Monday following a visit to see her son at the neonatal unit. That night she was found collapsed after a five-hour search.

Police, who are investigating, described her death as “unexplained, but not suspicious”. Cox had mistakenly entered a rarely-used stairwell in the hospital, according to reports.

In a statement Police Scotland said: “We can confirm that missing woman Amanda Cox was discovered collapsed within the Edinburgh Royal Infirmary around 10pm on Monday December 10. She sadly passed away a short time later.”

The statement continued: “Our thoughts and sympathies are with Amanda’s family and friends at this time.”

Jim Crombie, the deputy chief executive of NHS Lothian, said the health authority was assisting police with their inquiries.

“My thoughts and sympathies are with the family of Amanda Cox at this sad time,” he said.

A family friend said Cox had been suffering headaches since before the birth of her son last Thursday. “Apparently she was going back to her room for medication but took a wrong turning and came out of the neonatal ward into a disused ward,” the friend told the BBC.

Tributes have been posted on social media. “There are no words that will ever explain how i feel a great friend, team mate taken way too early in our hearts you will remain forever R.I.P Amanda Cox until we meet again, look after the boys from the rainbow bridge,” said David Wallace on Facebook.

Another person said: “A team mate, a class opponent, a true friend, I have no words in my tank, miss you but will never forget you.”

• The picture on this story was changed on 13 December 2018. The original image depicted the old Simpson Memorial Maternity Pavilion at the former Royal Infirmary of Edinburgh complex in Laurieston. The new image shows the Simpson Centre for Reproductive Health at the new Royal Infirmary of Edinburgh campus in Little France.