The mother of Queensland schoolgirl Tiahleigh Palmer says she is plagued by worry that those responsible for her daughter’s death are still at large and will hurt another innocent child.

Tiahleigh, 12, was last seen alive on October 30 last year when she was dropped off by her foster carer at Marsden State High School, Logan.

Her body was found in the Pimpama River six days later.

• Hundreds at Tiahleigh funeral
• Germanwings report: pilot urged to seek help
• Four Corners duo get support

In the four months since her death, detectives have found one of Tiah’s shoes and also offered a $250,000 reward for information that leads to an arrest, in addition to indemnity from prosecution.

But for her mother Cindy, one of the most important things is making sure another family doesn’t have to experience the same pain.

“It takes a vile human being to be able to take an innocent 12-year-old’s life,” she said on Monday afternoon.

“The first thing that comes into my mind when I’m going to bed at night (is) that this could happen to someone else.”

Ms Palmer last saw Tiah a week before her disappearance and said there was nothing unusual about her behaviour.

Cindy Palmer remembered her daughter Tiahleigh as a loving, caring girl who wanted to be a dancer. Photo: ABC

“She was good, she was her normal self: fighting with her brother, giving him a hard time.”

A missing person alert was issued six days after Tiah was last seen, just hours before an unidentified body was found by three fishermen on the banks of the Pimpama River.

A post-mortem examination was unable to establish Tiah’s cause of death and her backpack and uniform have never been found.

Police have expressed concern some people were holding back information because they were afraid of getting into trouble and Detective Superintendent David Hutchinson said that remained the case.

“We do have a number of positive lines of inquiry that we’re following,” he said.

“The people who did it should know that we’re not giving in.

“We have a team of detectives that are dedicated to finding out what happened, so they should never feel at ease.”

Ms Palmer remembers her daughter as a fun-loving, loveable girl with aspirations to become a dancer.

“She didn’t always get along with everyone but she was a very loving, caring person,” she said.

“She didn’t deserve what happened to her.”

-AAP