Alexandre Benalla attends a hearing by senators on September 19, 2018 in Paris after a video showed him wearing police uniform while attacking protesters during May Day demonstrations.
Paris CNN  — 

A former security aide to French President Emmanuel Macron has been placed in custody as part of an investigation into his use of diplomatic passports, the Paris prosecutor’s office told CNN on Thursday.

Alexandre Benalla was fired from Macron’s office in July last year after being filmed beating up a May Day protester.

He is currently under investigation for the “illegal use of a document certifying a professional position” and “forgery and use of forgery,” the prosecutor’s office said.

Macron’s chief of staff, Patrick Strzoda, on Wednesday testified at a Senate hearing that Benalla had used his diplomatic passports about 20 times between August 1 and December 31, 2018.

Strzoda also said Benalla had used a fake document with the letterhead of the President’s chief of staff to request his second service passport.

French President Emmanuel Macron leaves his house dressed for tennis with his then-deputy chief of staff Alexandre Benalla in June 2017.

Benalla used the passports on business trips to Africa, including to Chad, senators heard.

Speaking to Le Journal du Dimanche newspaper in recent weeks, Benalla said he had gained no improper benefit from the use of the passports.

“I may have been wrong to use these passports,” Benalla said in a December 30 interview. “But I did it only for personal comfort, to make it easier for me to travel in airports. I did not use them for my business, and I do not see what they could have done for me.”

Benalla also told the newspaper that he had returned his diplomatic passports to the Elysée Palace at the end of August but that they were given back to him with other personal effects in early October by “a member of the presidency.”

“Since they were given back to me, I did not see any reason not to use them.” Benalla said.

In a separate interview with digital outlet Mediapart, released on December 31, Benalla said he continued to have regular contact with the President on current affairs, such as the “gilets jaunes,” or yellow vest, protest movement.

“They cannot deny it,” Benalla told Mediapart. “It will be very hard to do because all these exchanges are on my mobile phone.”

The judicial inquiry into the May Day incidents is still ongoing, the Paris prosecutor’s office said Thursday.