DUBAI (Reuters) – A Qatari regulator said on Sunday it had fined First Abu Dhabi Bank 200 million Qatari riyals ($55 million) for obstructing an ongoing investigation into suspected market manipulation, a charge the bank later denied.

Qatar last year alleged that First Abu Dhabi Bank, the United Arab Emirates’ largest lender, made “bogus” foreign exchange deals to harm Qatar’s economy after the UAE and other Arab states began a boycott of Qatar in 2017.

The Regulatory Authority of Qatar Financial Center (QFC) began an investigation in March 2018 into the suspected manipulation of the Qatari riyal, Qatari government securities and related financial instruments.

Qatar has also asked U.S. regulators to investigate the U.S. unit of FAB on similar grounds.

In a statement on Sunday, the QFC regulator said the fine was a result of FAB’s failure to “provide copies of the relevant trading records and related documentation” needed for the investigation despite a Qatari court order to do so.

FAB has denied the market manipulation and said in a statement on Sunday that it had made “good faith efforts” to resolve the matter with the regulator and provide “all relevant and responsive information that it was required to disclose pursuant to QFC law.”

“Any allegations that FAB’s QFC branch failed to provide appropriate disclosures are false,” the statement said.

FAB said in June it was closing its sole branch in Qatar after the regulator placed restrictions on the bank that would prohibit it from undertaking new business.

“FAB is in the process of effecting an orderly wind-down of the QFC branch’s operations, following many months of baseless actions … that have made it impossible for FAB’s operations to continue in Qatar,” the FAB statement said.

Saudi Arabia, the UAE, Bahrain and Egypt started a trade and diplomatic boycott of Qatar in June 2017, accusing it of supporting terrorism, a charge Doha denies.

Qatar keeps its currency, the riyal, pegged at a fixed rate to the U.S. dollar, but saw it trade several percent weaker than its usual rate in offshore markets just after the dispute began.

The QFC regulator said that FAB could be subject to “additional disciplinary action” if warranted by its investigation and that it has the right to appeal the decision to the QFC Regulatory Tribunal.

($1 = 3.6408 Qatar riyals)