Cairo security forces arrested four people whom they claimed were in possession of explosive materials while allegedly on their way to the presidential palace.

A security officer in Heliopolis stopped the four while they were in a taxi. After searching them, the officer found a wooden box with 32 bottles holding a vinegar and ammonia mixture. The four were also in possession of a kilogram of nails and half a kilogram of dry ammonia.

Investigators say that the four admitted they intended to use the items as explosives.

The four suspects have been detained by police for four days pending further investigations.

Violent clashes have taken place around the presidential palace for a week between supporters and opponents of President Mohamed Morsy over the constitution referendum slated for 15 December and the constitutional declaration issued on 22 November. At least seven people have been killed and dozens more detained.

Newly-appointed Prosecutor General Talaat Ibrahim Abdallah also claimed Saturday that preliminary investigations had not yet uncovered what role, if any, the police played in the clashes.

At least 141 suspects have been interrogated in connection with the clashes, and eight others are also scheduled for questioning.

Edited translation from Al-Masry Al-Youm