Defence company Thales SA faces a bribery probe by French prosecutors into a $2.5 billion contract it won to modernize the Indian Air Force’s fleet of Dassault Mirage 2000 planes. 

A preliminary investigation has been opened into allegations by Sanjay Bhandari, who said in a court case that he served as a middleman to help Thales win the contract, according to a person familiar with the probe. The case focuses on whether payments to Bhandari were hidden bribes, the person said, who asked not to be identified discussing confidential matters.

Thales has never been questioned by prosecutors on the subject, a company spokeswoman said. Thales “strongly disputes” the allegations regarding alleged payments made by the company in connection with the project, she said.

A lawyer who represents Bhandari in London said he couldn’t comment on a probe in France.

Thales shares fell 3.5% to €132.00 at 3:11 p.m. in Paris. Dassault Aviation SA, which makes the Mirage planes and owns 25% of Thales, dropped 2.6% to €168.10.

France Info reported earlier Friday on the bribery investigation.

According to France Info’s report, Bhandari sued to recover money he says Thales still owed to him for helping it win the contract, a claim that was rejected by a French commercial court in October. 

Thales had no contract with Bhandari or his companies in connection with this project, the company spokeswoman said.