Shares in Oando fell close to a one-month low on Monday on news that regulators were investigating the firm’s shareholding structure following its $1.65 billion acquisition of ConocoPhillips’ Nigerian business, Reuters reports.

Shares in Oando, which are also listed in Johannesburg and Toronto, fell 9.54 percent in Lagos, down for the second session in a row, to a level last seen in June.

Oando acquired ConocoPhillips’s Nigerian business in 2014 aimed at moving the business upstream into oil exploration and production from being a petroleum products retailer. But high financing costs coupled with lower oil prices have hit profits, analysts say.