French authorities are looking into whether French cement maker Lafarge, which was taken over by Swiss rival Holcim in 2015, paid the Islamic State in 2013 and 2014 to keep its factories running in areas held by the terrorist group.

Prosecutors opened an investigation into suspected funding of terrorism in June 2017. They are looking into payments possibly made by Lafarge through intermediaries to armed groups, including Islamic State, and into possible purchases of raw materials from intermediaries related to these groups.

Eight former Lafarge executives were put "under formal investigation" for suspected terrorism financing, including Olsen and Bruno Lafont, who was Lafarge's CEO at the time.

The investigating magistrates decided to exclude Olsen from the process as they considered that he wasn't involved in the alleged acts that may constitute terrorism financing, Olsen's lawyer Pierre Cornut-Gentille said on Tuesday.

"This decision saves my honour and will allow me to resume with my career after fighting for several months to contribute to establishing the truth," Olsen said in a statement.

The case prompted Olsen, the first CEO after the merger, to step down and it remains a headache for LafargeHolcim, which has struggled to make the merger work and is cutting costs under the leadership of a new chief executive.

(Reporting by Emmanuel Jarry and Inti Landauro; Editing by Sudip Kar-Gupta)