The Office of the National Security Adviser (ONSA) has asked former Kaduna governor Nasir El-Rufai to submit any evidence supporting his claim that the office procured thallium sulphate, a highly toxic substance.
In a letter dated February 13, 2026, ONSA denied the allegation and said it had referred the matter to the Department of State Services (DSS) for investigation. The letter, signed by Brigadier-General OM Adesuyi on behalf of National Security Adviser Nuhu Ribadu, urged El-Rufai and other parties with relevant information to cooperate with investigators.
“I am directed to respectfully convey that ONSA has neither procured nor initiated any process for the purchase of such material, and has no intention of doing so,” the letter stated.
ONSA said the DSS will conduct a comprehensive probe and invite anyone with information to provide evidence.
The letter responded to El-Rufai’s earlier correspondence, dated January 30, 2026, in which he claimed that about 10 kilograms of thallium sulphate had allegedly been sourced from a supplier in Poland.
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Thallium sulphate is a colourless, odourless and highly toxic compound capable of killing humans in small doses.
Security personnel at El-Rufai’s Abuja residence initially refused to receive the letter when a dispatch clerk attempted delivery on Friday, citing the absence of the head of security.
Officials later delivered the letter successfully on Sunday, and the head of security signed for it on El-Rufai’s behalf.
El-Rufai recently said he accessed an intercepted telephone conversation involving Ribadu. Speaking on Arise Television, he alleged that someone tapped the NSA’s phone and that he heard instructions directing security operatives to arrest him.
ONSA has denied procuring thallium sulphate and maintains that the DSS investigation will establish the facts.
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