The Office of the National Security Adviser (ONSA) has instructed Nasir el-Rufai, former governor of Kaduna State, to forward proof of the alleged procurement of thallium sulphate to the Department of State Services (DSS) for further investigation, sources have told TheCable.
Thallium sulphate is a highly toxic, colourless and odourless compound capable of causing death even in small quantities.
In a letter dated January 30, 2026 and addressed to Nuhu Ribadu, the national security adviser, el-Rufai had said the substance was allegedly obtained from a supplier in Poland.
ONSA responded by dismissing the claim and requesting that he present any supporting evidence to the DSS for a detailed probe.
Sources informed TheCable that an initial attempt to deliver the response to el-Rufai’s Abuja residence was unsuccessful, as security personnel on duty reportedly declined receipt on Friday, stating that the head of security was unavailable and they were unsure of his next visit.
The letter was later successfully delivered on Sunday, with the head of security signing on el-Rufai’s behalf.
The correspondence, authored by OM Adesuyi, a brigadier-general, on behalf of the NSA and reviewed by TheCable, was dated February 13, 2026.
Adesuyi wrote: “I have the honour to present the compliments of the National Security Adviser and to acknowledge receipt of Your Excellency’s correspondence received on 11 February 2026 requesting clarification regarding the alleged procurement of approximately 10 kilograms of Thallium Sulphate by the Office of the National Security Adviser (ONSA). The correspondence further indicated that information concerning the purported procurement is reportedly available to the political opposition leadership. In this regard, 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. However, I am further directed to state that the allegation has been formally referred to the Department of State Services for a comprehensive investigation. Your Excellency and other parties involved, who may possess relevant information relating to this claim will be duly invited by the Service to provide any evidence that may assist in an in-depth investigation, establishing the facts and ensuring due diligence.
“Please accept the assurances of the esteemed regards of the National Security Adviser.”
On Friday, el-Rufai also said he accessed an intercepted phone conversation involving Ribadu.
Speaking on Prime Time, a programme on Arise Television, he claimed “someone tapped” Ribadu’s phone and that he heard the NSA allegedly instruct security operatives to arrest him.