UPDATE: Outlets are now reporting that a second explosion in Cairo has killed at least one person.

Original: A large bomb exploded in Cairo on Friday, directly in front of Egyptian police headquarters, killing at least two people. A spokesperson for the health ministry said that at least 40 people were also wounded in the attack.

The blast comes one day before the third anniversary of protests in Tahrir Square that toppled the Egyptian government and just days after an election that approved a new constitution for the country. Egypt has been in a period of relative instability since July, when a military coup ousted President Mohammed Morsi and the Muslim Brotherhood.

No person or group has yet claimed responsibility for the attack.