Malaysia's anti-graft agency, the Malaysian Anti-Corruption Commission (MACC), confirmed on Saturday that it's investigating allegations by Britain's Serious Fraud Office (SFO) that Airbus paid a bribe of 50 million U.S. dollars to win plane orders from Asia's largest budget airline group, Malaysia-based AirAsia which has rejected all allegations of wrongdoing in a statement.

Airbus declined to comment. The European plane maker admitted guilt and agreed to pay four billion U.S. dollars in a settlement approved on earlier Friday by courts in France, the U.S. and the U.K. after prosecutors said it had bribed public officials and hidden the payments as part of a pattern of worldwide corruption.

According to documents filed in the cases, the crimes spanned countries including Malaysia, Russia and China over 13 years. A French prosecutor said in court that the plan helped to boost the company's profits by 1.2 billion U.S. dollars.

The deal on Friday allowed Airbus to avoid criminal prosecution that could have led to it being barred from public contracts in the United States and the European Union.

Key decision makers in the alleged bribe case

The investigation comes as the Malaysian government evaluates five strategic investment proposals, among them one from AirAsia which runs an all-Airbus fleet of 274 planes.

The SFO's allegations concern a 2012 sponsorship agreement between the now-defunct Caterham Formula 1 racing team, founded by AirAsia boss Tony Fernandes, and Airbus's then-parent, EADS.

The SFO claimed that between October 2013 and January 2015, EADS paid 50 million U.S. dollars to sponsor Caterham, which was jointly owned by two people described as AirAsia Executive 1 and Executive 2. It said Airbus employees offered an additional 55 million U.S. dollars, though no payment was made.

Fernandes bought Caterham together with his partner Kamarudin Meranun, AirAsia's chairman, in 2011. Both of them can't be reached now.

The SFO said that Executives 1 and 2 were "key decision makers in AirAsia and AirAsia X, and were rewarded in respect of the order of 180 aircraft from Airbus".

"The payments to the sports team were intended to secure or reward improper favor by them in respect of that business."

The airline's statement said that "all negotiations and dealings leading to the signing of any aircraft purchase agreement have been undertaken directly with Airbus on an arm's length basis, and without the involvement of any third parties or intermediaries."

Malaysia has been trying for years to recover billions of dollars allegedly stolen here from the state fund 1Malaysia Development Berhad (1MDB).

Read more: What is the 1MDB scandal?

(With input from Reuters)