Hibernian managing director Rod Petrie has expressed the club's shock at the death of young player Liam O'Sullivan.
The 20-year-old died earlier on Monday. A post-mortem examination was due to be carried out on Tuesday in a bid to establish the exact cause.
It is understood police are investigating whether drugs and alcohol were involved.
The young defender had loan spells at Clydebank and Brechin City, but injury meant a lengthy spell on the sidelines from Hibs' under-21 side.
Petrie said: "Everyone at the club was stunned and saddened to hear of the death of Liam O'Sullivan at just 20 years of age.
"While we all feel a sense of loss, our thoughts and sympathies must go out to his family.
"Liam had begun to battle back to fitness following a long period of injury - and he had shown great character in doing so.
"He was working with both the club and his family to overcome his injury and some personal issues, and everyone who worked with him is devastated at his untimely death."