The Office of the National Security Adviser (ONSA) has denied claims that it procured approximately 10 kilograms of thallium sulphate, saying it neither purchased nor initiated any process to acquire the chemical, and has formally referred the allegation to the Department of State Services (DSS) for a full investigation.

In a letter dated and received on 11 February 2026, Brigadier-General O.M. Adesuyi, writing on behalf of the National Security Adviser, acknowledged receipt of correspondence seeking clarification about the alleged procurement. Adesuyi stated that ONSA “has neither procured nor initiated any process for the purchase of such material, and has no intention of doing so.”

Despite the denial, the office moved swiftly to escalate the matter to the DSS, asking the intelligence agency to conduct a comprehensive probe. The referral signals ONSA’s intent to treat the allegation seriously and to establish the facts through an independent inquiry, according to the letter.

The communication further indicated that the DSS will invite “Your Excellency and other parties involved” who may hold relevant information to provide evidence that could assist in an in-depth investigation. The invitation to stakeholders suggests the probe will seek documentary or testimonial proof to confirm or refute the claim and to ensure due diligence.

The letter concluded with formal assurances of the National Security Adviser’s regards. It was signed by Brigadier-General O.M. Adesuyi on behalf of the National Security Adviser of Nigeria.

The development raises questions about the source and motive behind the original allegation. Observers will watch closely for the DSS findings and any subsequent disclosures from ONSA or the parties expected to be interviewed, which could shed light on the genesis of the claim and whether any protocols or safeguards were breached.

Requests for comment to the Department of State Services and to the office of the National Security Adviser were not immediately returned.