The president of Nigeria’s upper house of parliament is to be investigated by lawmakers over allegations that he attempted to evade payment of customs duties on a car, after parliamentarians voted on Tuesday to examine the matter.

The allegations, which could lead to Senate President Bukola Saraki, Nigeria’s third-ranking official and a member of President Muhammadu Buhari’s party, being impeached if found guilty, are the latest in a series of such claims levelled at him. He has denied any wrongdoing.

Saraki still faces charges of falsely declaring his assets when he was a state governor from 2003 to 2011, to which he has pleaded not guilty.

The car duty allegations relate to newspaper reports that the Senate failed to pay import duties of 74 million naira ($240,650) on a bulletproof car worth 298 million naira. The reports said the car belonged to Saraki.

“We refer the matter to ethics and privileges (committee) to investigate, so that our colleagues would be cleared and this senate will stand as it supposed to,” said Ali Ndume, a senator who raised the motion to investigate Saraki.

The committee of lawmakers is expected to report its findings within four weeks.

“The allegation raised today by Senator Ali Ndume linking Dr. Abubakar Bukola Saraki to the importation of vehicle lacks basis as it was outright falsehood,” said Saraki’s spokesman, Yusuph Olaniyonu.

($1 = 307.5000 naira)

(Reporting by Camillus Eboh; Additional reporting by Alexis Akwagyiram; Editing by Hugh Lawson)