“There is no new attack but the fire broke out again. It began in some places not tended by firemen before,” Sawarmi Khaled Saad, the Sudanese army spokesman, was quoted as saying by the official SUNA news agency.
Residents of the area told AFP they saw smoke over the Yarmouk facility in the south of the capital Khartoum.
Explosions and fire spread through the Yarmouk compound at about midnight last Tuesday, after people in the neighbourhood reported an aircraft or missile had flown overhead.
The government, blaming Israel, said four radar-evading aircraft had attacked the plant which it said makes “traditional weapons.”
Official media say four people were killed, up from a toll of two initially given by the government.
Sudan accused the Jewish state of a similar raid 18 months ago, on its Red Sea coast.
Israeli officials have expressed concern about arms smuggling through Sudan and have long accused Khartoum of serving as a base of support for militants from the Islamist Hamas movement that rules the Gaza Strip.
Israel refused all comment on Khartoum’s allegations.
But a top Israeli defence official, Amos Gilad, said last week that Sudan “serves as a route for the transfer, via Egyptian territory, of Iranian weapons to Hamas and Islamic Jihad terrorists.”
On Saturday, a US-based non-profit monitoring group said craters at the scene of the explosion were consistent with the kind of damage created by the impact of air-delivered munitions.
The Satellite Sentinel Project started by Hollywood star George Clooney said satellite imagery showed six large craters, each approximately 16 metres (52 feet) across, at the Yarmouk plant.