BELLEVUE — Friends and neighbors are mourning a family of five, which included three children, killed in a duplex fire Friday as investigators try to find the cause of the blaze.

The fire in Bellevue killed Stephen Lasch, 41, Angela Lasch, 38, and their three children: son Noah, 11, and daughters Kayley, 6, and Hannah, 4, authorities said.

Hundreds of relatives, friends and neighbors gathered at a vigil Saturday near Bellevue Elementary School, where the older daughter was a first-grader.

First-grade teacher Sue Emery, who taught both Kayley and Noah, said both were happy children. She read aloud from a journal Kayley kept in her class, in which she wrote about how much she loved her family.

The crowd sang “Amazing Grace” and several tearful classmates of Kayley’s released five balloons into the cloudless sky.

Linda Lasch said her son had just started training Monday for a new job. Angela Lasch stayed at home to care for Noah, who was autistic, and Kayley, who used a feeding tube because of a congenital hernia.

“They were a wonderful family — one of the most loving, close families,” she said.

Angela’s mother, Debra Abraham, said the family had experienced loss before — a miscarriage in 2010. Angela spoke joyously about the prospect of seeing her baby again in heaven, Abraham said.