WEST BROOKFIELD — A mother and three children found dead Thursday in their home were murdered, Worcester District Attorney Joseph D. Early Jr. said Saturday.

Early, in describing the deaths as homicides for the first time, asked the public to help investigators locate a yellow plastic fuel can that they believe was taken from the Old Warren Road residence. He declined to elaborate on the significance of the can or say how the victims died.

“We need to speak to anyone who may come across a discarded yellow fuel can,’’ Early said during a news conference near the residence. His spokesman said such cans are commonly used to store diesel fuel.

Moses Bermudez, who lives at the home but spends time in California for his job, asked his father to check on his family after he couldn’t reach them by phone.

His father found the bodies of Sara Bermudez, 38, and their children, 8-year-old Madison, 6-year-old James, and 2-year-old Michael, in an upstairs bedroom, their bodies showing signs of burns.

Several fires had been set in the home but they had burned themselves out, an official said.

On Saturday, the road was closed to traffic. Yellow crime scene tape cordoned off part of the neighborhood and a State Police command vehicle sat near the residence.

Anyone with home or business surveillance video or footage taken from a motor vehicle dashboard camera in West Brookfield or along the Route 9 corridor is asked to contact State Police, Early said.

The public, he said, should be “vigilant and careful.’’

“Anything you see out of the ordinary, please call us,’’ Early said. “We think that the public should remain safe, careful, and vigilant with regards to this investigation.’’

At the home of Moses Bermudez’s father in Ware, a woman who came to the door said the family is grieving. The deceased are the grandchildren and daughter-in-law of her husband, she said.

“We’re looking for answers,’’ said the woman, who gave her name as Josefa. “It’s in the police’s hands right now.’’

She said her husband visited his grandchildren last week.

“They were wonderful little children and they didn’t deserve what happened,’’ she said.

On Friday, Moses Bermudez’s sister, Rachaul, described how her father found his slain relatives and called 911.

Her brother grew up in nearby Warren, but moved to California after high school and continues to travel there to work as an offshoreman, she said.

Moses and Sara Bermudez bought their home in West Brookfield about four years ago and together had launched a bouncy house business called MJM Jumpers, Rachaul Bermudez said.

In the Ware neighborhood where Moses Bermudez’s mother lives, a resident recalled meeting the oldest child, Madison, last year at a Christmas party.

“She was adorable, but smart,’’ said Mary Olsen. “She was beautiful.’’

At the party, the girl told Olsen she was learning multiplication tables in school and preparing for a test. Her father called Madison his “little princess,’’ Olsen said.

“I thought that was so adorable,’’ she said. “She was such a sweetheart.’’

On Thursday, she said she came home from a shopping trip and encountered Moses Bermudez’s mother, Anita, in tears.

“She just grabbed me,’’ Olsen said. “She says, ‘Moses’s wife and three kids are dead.’ She just kept crying.’’

Laura Crimaldi can be reached at laura.crimaldi @globe.com. Follow her on Twitter @lauracrimaldi.