Qatar banned the United Arab Emirates’ biggest bank from growing its business in the country amid an investigation into the potential manipulation of its currency.

First Abu Dhabi Bank PJSC ‘failed to comply with an order of the QFC Civil and Commercial Court to produce an affidavit demonstrating its preservation of documents relevant to an ongoing regulatory investigation into potential manipulation of the Qatari riyal,’ the Qatar Financial Centre Regulatory Authority said on its website.

The lender won’t be able to add new customers and engage in any regulated activities including deposit taking, providing credit facilities and arranging deals in investments, it said. The restriction doesn’t stop First Abu Dhabi Bank, which operates one wholesale banking branch in Doha, from continuing to provide services to existing customers.

Qatar’s central bank is investigating suspected attempts to devalue the riyal at the height of a diplomatic standoff with Gulf neighbours in 2017. The nation keeps the currency pegged to the dollar. But after Saudi Arabia, the UAE, Bahrain and Egypt accused it of backing terrorism — a charge Qatar denies — and imposed an economic boycott, the riyal came under pressure in the offshore market.