Hundreds of minors aged between 14 and 17 are serving illegal detention in a filthy prison in Banha, north of Egypt’s capital city of Cairo, a human rights organization says.

El Nadeem Center for Rehabilitation of Victims of Violence has shared information with the Times about the situation of hundreds of schoolchildren in a detention camp north of the Egyptian capital, Cairo.

According to the center, around 600 boys are being held in darkened prison cells, where they have no access to medical and legal care.

The prisoners have no access to clean water and sunlight as they are kept in a freezing underground facility.

The report cites evidence of boys suffering from various health problems. Some of them have undergone torture since the very beginning of their imprisonment. Egyptian officials have denied the existence of such a center altogether.

According to the Egyptian law, minors should serve their detention in juvenile centers. The law also stipulates that children must be provided with legal assistance.

The new revelations could further tarnish the image of Egypt’s military-backed government of Abdel Fattah el-Sisi, which continues his heavy-handed crackdown on followers of the deposed president, Mohamed Morsi, and his political party Muslim Brotherhood.

Morsi, the country’s first democratically-elected president, was ousted in July 2013 in a military coup led by Sisi, Egypt’s then head of the armed forces. Thousands of Brotherhood members, including the party’s senior leaders, have been arrested since Morsi’s ouster.

On Thursday, Human Rights Watch censured Egyptian authorities for referring hundreds of civilians to military courts based on a decree by Sisi.