Assistant fire marshal Willard Preston in Southern Sussex County said Thursday that investigators found a cooking pot on the stove of the house and a cut-up potato nearby.
Preston said it appears that one of the family members was heating cooking oil to make French fries and fell asleep.
A Delaware medical examiner has determined that all eleven died of smoke inhalation. Seven of the victims were children, ranging in age from infant to 9 years old.
Preston says there were two smoke detectors in the house, but the detectors had no batteries.
A 9-1-1 call was made from inside the house shortly before 3 a.m. Wednesday, but authorities say they have not yet determined which of the victims made that call.
The home was across from a cornfield in a tight-knit community where neighbors would often help the struggling family by donating food.
"The kids always had it rough," said Jocelyn Harmon, a neighbor and a substitute teacher who taught two of the children at a nearby elementary school. "It's just a small, very close-knit area where everybody helps everybody."
The fire came more than two months after a blaze killed a family of five in a beach house in a nearby city.
"This is about the worst I've ever seen in Delaware, or ever heard of," said the Rev. David Paul, chief chaplain of the Delaware Volunteer Firemen's Association and a firefighter for 47 years. "I think it's the worst in the state's history."
A day before the fire, the Sussex County Council voted to require all new homes to have hard-wired smoke detectors in every bedroom and to require detectors with battery backups on every floor. Investigators would not say whether the home that caught fire Wednesday had smoke detectors.
William Wright, standing stunned across the road from the home, said the victims included his daughter, 28-year-old Jacquelin; her five children, ranging from an infant to a 9 year old; Jacquelin's mother, Eltama Shelton; and grandmother Evelyn Shelton.
Also killed were Jody Wright, 51, Eltama Shelton's daughter, and her two children, family members said.
Quintin Odums, whose children Jeremy, 9, Latosha, 6, and Tae, 5, were killed in the fire, was told of the tragedy when he reported for work Wednesday at a poultry processing plant.
He said he had talked to his children by telephone the night before.
"They told me, 'OK, I love you, Dad'," he said.
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