A Moncton woman who is wanted on a Canada-wide warrant in connection with the murder of Baylee Wylie "could be anywhere," say RCMP.

Marissa Shephard, 20, has managed to elude police for more than three weeks, while two of her co-accused and an alleged accessory after the fact are now behind bars.

Marissa Shephard, 20, of Moncton

Marissa Shephard, 20, of Moncton, is wanted on a Canada-wide warrant on charges of first-degree murder and arson in connection with the death of Baylee Wylie. (RCMP)

The young mother, whose appearance seems to change dramatically, based on the released photographs of her, is only five-foot-five and weighs only 100 pounds, but is considered dangerous by police due to the violent nature of Wylie's death.

The 18-year-old's body was discovered after an early-morning house fire on Sumac Street on Dec. 17.

Shephard is charged with first-degree murder and arson in the case.

"At this time we don't know where Marissa Shepard is," said RCMP Const. Jullie Rogers-Marsh.

"We're still actively searching for her, she's continued to be sought by RCMP. Really she could be anywhere," she said.

Tyler Noel and Marissa Shephard

Tyler Noel,18, was arrested over the weekend, but Shephard remains at large. (RCMP)

Shephard's family is also awaiting news of her whereabouts, according to her grandfather.

David Carson says he's concerned for his granddaughter, but feels everyone is doing everything possible to find her.

"Life is complicated," he said.

Shephard's mother, Christine Carson, could not be reached for comment, but her partner told CBC News the family is co-operating with authorities.

Shephard's co-accused, Tyler Noel, who was also wanted on a Canada-wide warrant and believed at times to be with her, was captured over the weekend.

Marissa Shephard

The comment under Marissa Shephard's Facebook photo above reads, "BTW - (NotRealGun) Just Saying before anyone thinks anything." (Facebook)

RCMP were called to a break-in at a cottage in Elgin on Saturday around noon. That led police to Petitcodiac where they arrested Noel in a car, along with two other people.

Noel, 18, is charged with first-degree murder and arson in connection with Wylie's death.

Zachary Holden, 18, of Moncton, who is accused of assisting Noel, is charged with being an accessory after the fact to murder, being unlawfully in a dwelling house, flight from police and dangerous driving.

Bradley John Bonnell, 20, of Wheaton Settlement, is charged with being unlawfully in a dwelling house.

Noel, Holden and Bonnell all remain in custody and are scheduled to appear in Moncton provincial court on Thursday.

Marissa Shephard

Shephard, who can appear much younger with her hair pulled back and no makeup on, is considered dangerous, according to the RCMP. (RCMP photo)

Devon Morningstar, 18, who was previously charged with first-degree murder and arson in connection with Wylie's death, has been sent for a 30-day psychiatric assessment.

Shephard is described as being Caucasian, with brown eyes and brown hair. She has a tattoo with the name Stephen on her neck and a tattoo of a crown on her chest — not a heart as had been stated in previous news releases.

Anyone helping her hide could face serious charges, police have said.

Anyone with information about her whereabouts is asked to immediately call 911, the Codiac Regional RCMP at 506-857-2400, or Crime Stoppers at 1-800-222-TIPS (8477).