(CNN) -- The Tanzanian island of Zanzibar began three official days of mourning Sunday, a day after 200 people died when a ferry jammed with passengers and tons of cargo capsized amid strong waves.
In addition to Tanzania, South Africa was sending divers and navy forces to help with recovery efforts, said Mohamed Aboud, the state minister of Zanzibar.
British officials have also sent helicopters to help with the search efforts.
"Right now, we are focusing on getting the bodies for the relatives, but you never know, God is God ... we might find people alive," he said.
Rescuers saved 579 people, including 20 children, Aboud said.
"A lot of children are going back to Zanzibar for school, so there were a lot on the ferry," said Ismail Katumba, a resident of Dar es Salaam. "It was so chaotic. It was so crowded."
The minister said the ferry carries a maximum capacity of about 600 people and was traveling between the islands of Zanzibar and Pemba.
But additional passengers, who were apparently not registered, had also made their way onboard, he said.
It capsized in predawn hours local time, sending passengers scrambling for any available objects to avoid getting swallowed by the dark waves, witnesses said.
Some jumped atop mattresses floating from the cargo.
Fisherman, local hotels and residents joined rescue crews to help in the search, authorities said.
Rescue crews took bodies to a nearby tent.
"You could hear people screaming loud and crying as bodies surfaced, mostly children," said Katumba, who lost a friend in the accident. "What you do is you just go over and start looking at the bodies to identify them."
Most of the rescued were transported to local hospitals for treatment, and some have been discharged.
President Ali Mohamed Shein of Zanzibar, who ordered the three days of mourning, also called for flags to fly at half staff.
Tanzanian President Jakaya Kikwete also said the nation would mark three days of mourning starting Sunday.
The government has buried dozens of unidentified victims, the minister said, and will maintain records for those searching for loved ones.
Pemba and Zanzibar, the two main islands on the Zanzibar archipelago, are popular among tourists for their pristine sandy beaches on the Indian Ocean.
Zanzibar is a semi-autonomous part of Tanzania.
CNN's Jim Clancy, Nicole Saidi, Samira Said and journalist Richard Mgamba contributed to this report