The Acting Chairman of the Economic and Financial Crimes Commission (EFCC), Ibrahim Magu, has said the investigation of Senate President Bukola Saraki is not based on personal motive.
He said the commission only invites people it suspects of corruption-related crimes.
Mr Magu spoke on Tuesday with journalists after receiving an award at the commission's conference room at its headquarters in Abuja.
The Outstanding Leadership in Public Service award was presented to him by the Euro Knowledge Group.
Asked why the EFCC was reopening investigations into old cases against Mr Saraki, the EFCC chairman said, "No it is not personal, we are not after anybody. His case is not different from other individuals that are being investigated."
He said the commission does not witchhunt any government official irrespective of their political background.
"'The EFCC does not pursue people who do not have corruption cases. If you are not corrupt, we do not invite you. If you are not a 419 or internet fraudster, we would never invite you.
"We do our homework very well. Sometimes we conduct our investigations for up to six months, we have been investigating people for more than five years.
"Corruption is a national disaster, every Nigerian should fight corruption, whether you are in Nigeria or outside the country. You remove corruption, you eradicate disaster. All these banditries and Boko Haram, the root is corruption," he said.
The EFCC on Sunday marked some properties at 15a, 15b and 17 MacDonald Road, Ikoyi, Lagos allegedly belonging to Mr Saraki.
Reacting through a statement on Sunday by his media aide, Yusuph Olaniyonu, Mr Saraki said the agency was only investigating what it had once probed.
Mr Saraki tagged the agency as being 'mischievous.'
The recent effort by EFCC to probe Mr Saraki started when the agency wrote a letter to the Kwara State Government for a breakdown of his income and entitlements as governor of the state.
The anti-graft agency urged the former Kwara state governor not to be shaken "so long as he has no skeletons in his cupboard.