Mario Romain pleaded not guilty at the Montreal courthouse Monday afternoon, after he was formally charged with the first-degree murder of Cinthia Toussaint.

The 26-year-old is Toussaint's ex-boyfriend and the father of her three-year-old son. He was arrested Saturday afternoon, five days after Toussaint mysteriously disappeared.

A passerby spotted the corpse of a black woman Saturday morning inside a sewer in a parking lot at the corner of Louvain St. E and Papineau Ave. in St. Michel -- just a block from where Toussaint was supposed to meet Romain at the beginning of the week.

Toussaint had told a friend she was going to meet Romain at the Taz skateboarding park May 17, in the early morning hours.

Romain told police she never showed up for the meeting.

A coroner is scheduled to begin an autopsy on the body Tuesday.

The identity of the body will not be confirmed until the coroner completes a report, which is expected to take at least a week.

But police have informed the Toussaint family that it is almost undoubtedly the 23-year-old's body.

Family devastated

Grief-stricken family members and friends, still struggling to come to terms with the gruesome discovery, told reporters Toussaint was a loving mother who was stuck in an abusive relationship.

"It's very, very hard," said longtime friend Flora Senat. "They were always fighting, that's what she was telling me."

Toussaint's mother, Marie-Ange Auguste, was distraught as she walked out of the courtroom, holding Cinthia's graduation photo.

"He left a baby that I have to take care of now, and he took my baby," she said.