The Office of the National Security Adviser (ONSA) has asked Nasir el-Rufai, a former governor of Kaduna State in northern Nigeria, to present any evidence he has regarding claims of an alleged procurement of thallium sulphate to the Department of State Services (DSS) for investigation.
Thallium sulphate is a highly toxic, colourless and odourless chemical compound capable of causing death in very small doses.
The directive followed a letter dated January 30, 2026, in which el-Rufai wrote to Nuhu Ribadu, Nigeria’s National Security Adviser, alleging that about 10 kilograms of the substance had been sourced from a supplier in Poland.
In its response, ONSA rejected the allegation and stated that it neither procured nor initiated any process to procure thallium sulphate.
Instead, the office said the claim had been referred to the DSS for a full investigation, requesting that el-Rufai and any other individuals with relevant information cooperate with security agencies.
Okay News reports that the response from ONSA was initially returned undelivered after security personnel at el-Rufai’s Abuja residence declined to accept the letter on Friday, citing the absence of the head of security.
The correspondence was eventually delivered on Sunday and formally received on his behalf.
The reply, dated February 13, 2026, was written by Brigadier-General OM Adesuyi on behalf of the National Security Adviser. In the letter, Adesuyi stated:
“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.”
