The British wife of French presidential candidate Francois Fillon is facing preliminary charges over well-paid parliamentary jobs that investigators suspect she never performed.
Mr Fillon himself has already been charged in the case, which has deeply damaged the conservative candidate's chances in the two-round election on April 23 and May 7.
He is suspected of embezzlement and other charges.
Penelope Fillon, from Abergavenny in Wales, is expected to face investigating judges on Tuesday in Paris who can hand her preliminary charges in the case.
Investigators recently expanded the probe on suspicions that the couple falsified documents after the investigation opened to prove that Mrs Fillon carried out parliamentary work for her husband.
The Fillons have denied wrongdoing.
Mr Fillon, once the front-runner, has called the investigation a smear campaign to torpedo his presidential bid.