Shares in Nigeria’s Fidelity Bank shed 2.5 percent on Friday after the Economic and Financial Crimes Commission said it had arrested the  bank’s chief executive, Nnamdi Okonkwo as part of an investigation into transactions made in the run-up to elections last year.

Okonkwo, Fidelity CEO  and the operations director have  been in custody  since Wednesday, the agency said on Thursday.

Fidelity Bank said in a statement on Thursday that “the transactions were duly reported as required by the regulators” and it was cooperating with authorities.

Nigeria’s former oil minister, Diezani Alison Madueke laundered $115 million through the bank in March 2015 to buy officials of the Independent National Electoral Commission to write poll figures for former President Goodluck Jonathan.

The money was converted into Naira and distributed to senior INEC officials countrywide to rig the election.

Some INEC officials have been arrested and some have refunded some money to EFCC.  Fidelity was reported to have returned N49million to EFCC,  its profit from the illicit transaction.