HICKORY, N.C. — Investigators indicated Tuesday they believe someone killed a 10-year-old girl with disabilities who was reported missing over the weekend, and accused her stepmother of trying to throw off investigators with a fake ransom note.

Police said the search for Zahra Clare Baker has shifted to a homicide investigation, canceling a missing child alert for the shy but upbeat girl who used hearing aids and a prosthetic leg because of bone cancer.

The girl’s stepmother, Elisa Baker, is the only person accused in the case so far. Hickory Police Chief Tom Adkins said she was charged with felony obstruction of justice after admitting she wrote the note, which asked for $1 million.

Complaints filed in court by a relative and neighbor in recent months portray Elisa Baker as nasty-tempered and willing to use a gun or her fists to settle arguments.

“It was unreal. She didn’t get along with anyone in the neighborhood,” said former neighbor Karen Yount, who filed one of the complaints.

At a news conference, Adkins said police can’t find anyone outside the household who has seen Zahra alive in the last month. That uncertainty has stymied efforts to search for her, despite offers from volunteers in the city of 40,000 about 50 miles northwest of Charlotte.

“We understand the public wants to help find Zahra. The problem is we cannot confirm with any confidence how long Zahra has been missing,” he said. “Without this information, we cannot positively select the area to search for her.”

Adkins did not take any questions or further explain why the case was being treated as a homicide probe. A search warrant revealed on Monday that police dogs detected the smell of human remains on cars belonging to the father and stepmother.

Adkins said Elisa Baker has asked for an attorney, but none had been assigned late Tuesday.

The girl’s father, Adam Baker, has not been charged in the case, though the chief said previously he hasn’t been ruled out as a suspect.

The stepmother said she last saw Zahra sleeping in her room Friday.