At least 1,000 people were injured in the violence on Wednesday when fans invaded the pitch after local team Al-Masry beat Cairo-based Al Ahli, the most successful club in Africa.
Most of the deaths were among people trampled in the crush of the panicking crowd, while others fell or were thrown from terraces.
The incident was Egypt's worst football disaster and the country's football association (FA) board have been sacked by Prime Minister Kamal al-Ganzouri.
FIFA President Sepp Blatter wrote to the head of the Egyptian FA Samir Zaher offering his condolences and support.
"I would like to join your country and the football family in mourning the death of the dozens of Egyptian football fans and others at last night's match in Port Said," the letter said.
"Today is a black day for football and we must take steps to ensure that such a catastrophe never happens again. Football is a force for good and we must not allow it to be abused by those who mean evil.
"As discussed by telephone this morning, I await further news from you concerning the circumstances of this tragedy."
Angry Egyptians clashed with security forces on Thursday during protests against the army-led government for failing to prevent the deadliest incident since the overthrow of President Hosni Mubarak last year.
Some saw the violence as orchestrated to target the "Ultras", Al Ahli fans whose experience confronting police at football matches was turned with devastating effect against Mubarak's security forces in the uprising.
The Supreme Council of the Armed Forces, headed by Mubarak's long-time defence minister, Field Marshal Mohamed Hussein Tantawi, vowed to track down the culprits and declared three days of national mourning.
Egypt's FA said it was indefinitely postponing matches in the premier league. Al Ahli club suspended all sports activities and declared three days of mourning.
