International rights watchdog Amnesty International has called on Egyptian authorities to order police to stop intimidating the family of a Salafi preacher allegedly tortured to death in a detention center in Alexandria earlier this month.

Sayyed Bilal, 31, was among dozens of Salafi Muslims arrested by State Security Investigation officers for possible links to a suicide bombing that rocked the Church of St. Mark and St. Peter in Alexandria on New Year’s Eve, killing 23 Coptic Christians.

Bilal was detained on 5 January by State Security Investigations (SSI) officers, and was found dead the next day. His body was turned over to his family bearing signs of torture, family members said when filing a complaint with the Alexandria District Attorney's office.

"Since filing the complaint and speaking to the media, Sayyed Bilal’s family has faced increasing intimidation from SSI officers," said London-based Amnesty International in a Tuesday press release.

“Both the death of Sayyed Bilal and the reported threats against his family are very disturbing developments and point to a continuing pattern of unlawful behavior by the SSI, which has long been accused of using torture,” said Malcolm Smart, Amnesty International’s director for the Middle East and North Africa.

“The Egyptian authorities must take immediate measures to protect the family, ensure an independent investigation into Sayyed Bilal’s death, and safeguard other detained suspects from torture or other ill-treatment.”

Local media also reported that another young man had been detained since the church bombing.   

On Monday, the public prosecutor ordered an investigation into the whereabouts of Mohamed Ismail Mahmoud, who was also arrested on 5 January by SSI officers in connection with the church bombing and who was detained, like Bilal, at Alexandria's Al-Labban Police Station.

Alexandria is considered a stronghold for Salafis, who are often blamed for inciting anti-Christian sentiment through religious sermons and television programs. Dozens of them were arrested in the attack's aftermath.

"An unknown number are being held incommunicado and are at serious risk of torture," stated Amnesty International.

Bilal's family has been summoned twice by the SSI and threatened with detention.

Plainclothes police have been stationed around the family home to prevent them from meeting with human rights workers and journalists, according to Amnesty International.

“This harassment and intimidation must stop, and stop now,” said  Smart. “The Egyptian authorities should be leaving no stone unturned to find the truth about what caused an apparently fit and healthy man to die within hours of his arrest.”

Alexandria's district attorney ordered an autopsy to be conducted on Bilal's corpse. While the autopsy has already been carried out, its findings remain unknown.

“If Sayyed Bilal was tortured to death, those responsible must be brought to justice. SSI officials should not be afforded immunity, as so often seems to have been the case in the past,” said Smart.

In recent years, Egyptian police have frequently been accused of using torture and ill-treatment against detainees. While some policemen have been slapped with jail sentences for torture, no SSI officer has ever been convicted of the crime, according to Amnesty.