The Economic and Financial Crimes Commission (EFCC) operatives are searching the Abuja residence of Shehu Sani, a former senator.
A source said the officials arrived at the residence located in Wuse 2, Abuja, around 3:30 pm.
The anti-graft agency arrested Sani last week over alleged extortion.
Sani, who represented Kaduna central senatorial district between 2015 and 2019, allegedly collected money from Sani Dauda, owner of ASD Motors, promising to pass it on to Ibrahim Magu, acting chairman of the anti-graft agency.
He also reportedly said he could assist Dauda in influencing the outcome of some cases using his connection with the chief justice of Nigeria and some other judges.
The CJN had distanced himself from Sani, saying he has never had anything to do with the former.