Newly reviewed military documents, messages and videos indicate that Sudan’s armed forces built a secret stockpile of chlorine-based chemical munitions and used some of them against the Rapid Support Forces (RSF), according to an investigation published by The Washington Post on Saturday.

The material reviewed by the newspaper includes evidence of weapons testing, alleged production facilities and communications between military officials. It also indicates that as many as 290 chemical munitions may have been stockpiled, while separate messages suggest 106 bombs had been used.

The documents point to the use of chlorine in attacks around the Al Jaili oil refinery and Garri military base north of Khartoum in 2024. Earlier investigations by France 24 and C4ADS had identified industrial chlorine containers at the sites and found evidence consistent with their use as improvised chemical weapons.

One document reviewed by The Post describes a so-called “dual-effect” bomb containing 15kg of gas and 20kg of explosives. Other material allegedly shows efforts to modify the weapons and conceal evidence of chemical use.

The files also contain messages attributed to Sudanese military officer Tariq Madani, whom regional security officials described as a leading figure in the alleged programme. The messages refer to chlorine supplies, weapons production and the arrival of 20 large tanks through Egypt, while another set of messages claims the programme could theoretically produce up to 1,100 bombs.

The investigation also links Madani to communications with Sudanese leader Gen Abdel Fattah al-Burhan. One message from 2025 allegedly sought to reassure Burhan that a military site used to store weapons had been “emptied of traces and residue”. A document bearing Burhan’s signature later included Madani in a government investigation into the chemical weapons allegations.

The Post said digital forensics experts found no indication that key audio, photographs and videos it examined had been manipulated. The analysis did not, however, independently establish that the claims made about what the material depicts were correct.

The allegations come after the United States determined in April 2025 that the Sudanese government had used chemical weapons in violation of international law. Washington imposed additional sanctions in June 2026 after concluding that Sudan had not met conditions required to return to compliance with the Chemical Weapons Convention.

Sudan has repeatedly rejected the allegations. In July, its foreign ministry said the government remained committed to the Chemical Weapons Convention and argued that US sanctions were based on accusations unsupported by material or technical evidence. Sudan has also said a national investigation found no evidence of chemical or radioactive contamination.

The Organisation for the Prohibition of Chemical Weapons (OPCW) says the Chemical Weapons Convention requires states never to develop, produce, stockpile or use chemical weapons. Sudan has been a party to the convention since 1999.

The new material adds substantially to the evidence previously made public about alleged chlorine use in Sudan, but independent verification of the full programme would require access to the sites, physical evidence and witnesses inside the country.