The two children found dead in their Zimmerman home Sunday were drowned and their mother’s death has been ruled a suicide pending further investigation and toxicology reports, the Sherburne County Sheriff’s Office said Tuesday.

The bodies of Stephanie Shields, 35, and her children Nolan, 7, and Josephine, 6, were found Sunday morning by a relative and a neighbor, who came to the home to check on them, authorities said. The sheriff’s office reiterated Tuesday that no suspects are being sought, suggesting the deaths are a case of murder-suicide.

As a local bank prepared to set up a memorial fund, the staff at the Zimmerman Elementary School met early Tuesday and engaged in “crisis planning” for the day. Both children attended the school, which was resuming classes after a spring break that concluded on Monday. Nolan was a second-grader. Josephine was in kindergarten.

“The kids are in classes, learning and in a safe environment,” said Jana Hennen-Burr, assistant superintendent for educational services for the Elk River School District.

“We’ve provided resources for them,” Hennen-Burr said. “We have a crisis team. We’re going from classroom to classroom. We’re a large district. We’ve had tragedies in this district before.”

Shields’ husband and the children’s father, Mark Shields, moved out of the house in the 13300 block of 5th Avenue S. last week, Brott said.

Mark Shields is a sergeant first class in the Minnesota National Guard, serving as readiness noncommissioned officer for the 850th Horizontal Engineer Company in Cambridge. He has served in the Guard since 1989 and was deployed to Iraq from September 2004 to November 2005.

Outside the Shields’ home on Tuesday, people left flowers, balloons and other objects in a spontaneous memorial.

The Sheriff’s Office would not speculate about what might have led to the deaths of the three family members, who were seen often in the neighborhood.

Like others on the street, a neighbor who is caring for the Shields’ dog remained in shock over news of the children’s drowning and their mother’s apparent suicide.

“Those kids were her world,” the neighbor said. “She did everything for them.”

The Sheriff’s Office said it will be exploring “toxicology testing, lab results and electronic communications records” as part of the investigation.

Stephanie Shields worked in the human resources department at Fairview Health Services.