Police spokesman Emmanuel Ojukwu told the BBC that Interpol was being contacted because of a court order requesting the men's extradition.
Ribadu was removed from his post and sent on a year's "training course" shortly after Obasanjo left office in 2007.
After the course he fled to the UK, as he said two attempts were made on his life.
He was subsequently accused of not declaring his assets while in office, something he denies.
el-Rufai went to study in the United States after leaving office in 2007 and is wanted for questioning by the EFCC over the alleged disappearance of millions of dollars of government funds.
Critics say the cases against the men are politically motivated.
President Umaru Yar'Adua won elections in 2007 after Obasanjo stood down after two terms.
He was chosen to contest the polls by his predecessor, but his administration has since sought to remove the influence of ex-President Obasanjo in government.
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