Egypt's prosecutors order the arrest of two policemen for questioning over the death of 37 supporters of toppled Islamist president Mohamed Morsi while they were in custody.
Egypt's interior minister says a forensic report reveals the men died from asphyxiation in the back of a crammed police van after police fired tear gas to thwart a mass jail escape.
More than 600 suspects were being transported to the Abu Zabaal prison on the outskirts of Cairo when they took an officer hostage, prompting police to fire rounds of tear gas to free him.
Also summoned for questioning are two unidentified victims being treated at a hospital and a policeman.
The Muslim Brotherhood, who fielded Morsi for presidency, has called for an international investigation into what they called a "heinous crime."
The incident affirms "the systematic violence aimed at opponents of the coup, and the cold-blooded murder they are subject to" says the Islamist group.
Egypt has been hit by a wave of unrest when police Wednesday forcibly broke up two sit-ins that had been protesting Morsi's ouster for six weeks. Brotherhood and allies replied with nationwide protests that turned into clashes, plunging the country into deeper turmoil. At least 800 people died in the dispersal and days of ensuing clashes between supporters of the Islamist leader and security forces.
Hours after the bloodshed, suspected Islamist militants killed 25 policemen near the Israeli border in the lawless Sinai Peninsula, heightening fears of spiralling violence since Morsi's ouster on 3 July.