JUBA, South Sudan -- The death toll rose to 193 in South Sudan's fuel tanker explosion Saturday as the government declared three days of mourning.

More patients have succumbed to their injuries, said Patrick Raphael Zamoi, the governor of Western Equatoria state where the explosion happened Wednesday.

Hundreds of people had gathered to scoop gasoline from a leaking truck which had veered into a ditch outside Maridi town when the tank exploded under unclear circumstances.

Zamoi told The Associated Press the death toll is likely higher because the official count only includes those who died on the spot or in hospital. Others may still be unaccounted for or may have died at home, he said.

Thirty new badly burned patients have arrived at Maridi hospital, and two helicopters carrying a ton of supplies and another surgeon have been dispatched from the capital Juba, said Layal Horanieh of the International Committee of the Red Cross.

The Ministry of Health made an urgent public appeal for blood donations to treat injured patients who were evacuated to Juba for better care.

Survivors told AP there was a shortage of medical staff in Maridi because people had fled recent clashes involving the national army. Heavy gunfire between the army and unknown gunmen continued Thursday in a nearby area of Western Equatoria, the UN said.

Deadly fuel tanker explosions are common in East Africa, where poor residents living near highways converge around fuel tankers after accidents to steal gas.