Thirteen people held for more than 18 years without trial in Eritrea have been released from a notorious military prison, relatives of the detainees have told the BBC. Among those freed were several prominent figures, including 69-year-old Olympian cyclist and businessman Zeragaber Gebrehiwot. They had been held at Mai Serwa prison, known for its harsh conditions and where many of the inmates are believed to be political prisoners. An unnamed source who was once detained in Mai Serwa told the BBC that the prisoners were arrested in October 2007 following an assassination attempt on Col Simon Gebredingil, a senior internal security officer in President Isaias Afwerki's government. Around 30 people were initially detained, and although some have been released over the years, about 20 remained in custody. Zeragaber competed in the Moscow Olympics in 1980 when Eritrea was part of Ethiopia. The mountainous country gained its independence from Ethiopia in 1993 and has a strong cycling culture that has garnered international recognition in recent times. The release comes amid growing international scrutiny of Eritrea's human rights records, with many prisoners reportedly suffering health issues. Families were not allowed to visit prisoners during their detention. The Eritrean government has yet to make any official comments regarding this release, raising further questions about the circumstances surrounding it. Human rights organizations have long condemned the Eritrean government for gross human rights violations, including torture, forced disappearances, and imprisonment of thousands under inhumane conditions. Mai Serwa prison has been criticized for expanding its detention facilities, which now include 20 metal shipping containers where prisoners are held incommunicado. The fate of many other detainees, including those arrested during the infamous G-15 incident and independent journalists, remains unknown.