The Economic and Financial Crimes Commission has invited Deputy Senate President, Ike Ekweremadu, for questioning.
A July 24 letter to Mr Ekweremadu said he was under investigation for alleged conspiracy, abuse of office and money laundering.
Mr Ekweremadu had been under investigation by the EFCC for allegedly owning questionable properties abroad.
He was also arraigned for allegedly forging Senate standing rules to pave way for the emergence of Bukola Saraki as Senate President in June 2015.
The charges on alleged forgery were later dropped by the federal government.
The letter to Mr Ekweremadu, which was shared by Mr Saraki’s aides moments ago, came hours after EFCC operatives joined State Security Service officers to lay a siege to the home of the Deputy Senate President.
The siege was said to still be ongoing as at 11:30 a.m. at the Apo Legislative Quarters residence of the top lawmaker.
“This commission is investigating the above mentioned case in which your name feature prominently and the need to obtain certain clarification from you become imperative,” said the letter which was signed by the EFCC’s director of operations.
It added that the request is brought pursuant to Section 38 (1) of the EFCC Act.
Mr Saraki said on the floor of the Senate Tuesday that security agencies were being used by President Muhammadu Buhari to bully All Progressives Congress lawmakers who planned to abandon the ruling party in a mass defection today.
Mr Saraki was also briefly prevented from going out of his home by security agents, but reports said the siege was short lived after officers realised the top lawmaker had outsmarted them and escaped.
Mr Saraki later turned up at the Senate and convened plenary after 10 a.m. Within a few minutes after the Senate convened, about 15 senators were announced to have decamped from the APC, effectively making the party a minority at the upper chamber.
Mr Saraki himself did not announce his cross carpeting, although he is widely expected to make the move any day now, especially since the APC has become the minority party.
The police on Monday night summoned Mr Saraki to appear at 8:00 a.m. for questioning by homicide detectives over the killings that occurred during the April 5 robbery attack in Offa, Kwara State.
Mr Saraki appeared to have ignored the police invitation when he realised that Mr Ekweremadu, who should have presided over plenary in his absence, was being prevented from going out of his home.