Ex-partner of missing Minnesota mom arrested in connection with her disappearance

The ex-partner of a Minnesota mother who has been missing since March under suspicious circumstances has been arrested in connection with her disappearance after human remains were found amid the investigation, authorities said.

Madeline Kingsbury, 26, was last seen the morning of March 31 when she and her children's father dropped their two young children off at a day care before returning to her home in Winona, according to Winona Police Chief Tom Williams. The children's father, Adam Fravel, told police he left the house in Kingsbury's van around 10 a.m., but when he returned later that day, Kingsbury was not there, Williams said.

Amid the search for Kingsbury, a Fillmore County deputy found human remains Wednesday afternoon in brush off Highway 43, north of Mabel, Minnesota, "and was located using information generated during the Madeline Kingsbury investigation," the Winona Police Department said in a social media post Wednesday night.

"Because of this, law enforcement personnel have arrested Adam Fravel on probable cause in connection to her disappearance," the department said.

Authorities are "working as quickly as possible to positively identify the remains," it added.

The Winona Police Department has scheduled a press briefing at 1 p.m. local time Thursday to discuss the case.

Early in the investigation, Williams said police believed Kingsburgy's disappearance was "suspicious" and "involuntary," and that they were concerned for her safety.

There was no indication Kingsbury left home on foot or in another vehicle, and her cellphone, wallet and ID were found in the house, according to Williams.

The day she went missing, Kingsbury did not show up for work and did not respond to "numerous" calls and messages from friends and family and failed to pick up her children from day care that afternoon, which is "extremely out of character for her," police said.

Her disappearance has prompted thousands of volunteers to help in the search.

In the weeks after she was reported missing, Fravel denied having anything to do with her disappearance.

"Over the course of the last 12 days, my family and I have been subject to a myriad of accusations regarding the disappearance of the mother of my children," Fravel said in a statement released by his attorney on April 14.

He said he has been cooperating with authorities and that investigators advised him not to attend press conferences or searches "due to safety concerns."

Kingsbury's family is offering a $50,000 reward for information leading to her whereabouts.

"Please help us find Madeline," her sister, Megan Kingsbury, said during emotional comments at a press conference in April. "Her children need their mother. We need our daughter, our sister, our aunt and our best friend back."

Her sister described Kingsbury as a "hard-working and dedicated mother" who works for the Mayo Clinic and is a graduate student.

ABC News' Will McDuffie contributed to this report.