A Toronto police officer said Tuesday he has heard "disturbing" third-hand information about the life of a seven-year-old girl who was found dead on Sunday, and now he's pleading for people with first-hand knowledge to come forward with details.

Katelynn Sampson, 7, looked as though she might have been abused for some time, police said Tuesday. (CBC)

Det. Sgt. Steve Ryan said he doesn't want to disclose the details until they are confirmed, but he said there are suggestions that young Katelynn Sampson was abused for some time.

"I can only tell you from what I observed as a non-medical person, that some of those injuries did not appear to be fresh injuries," he told reporters in Toronto.

Ryan said when emergency workers found Katelynn's body in an apartment in the west-end neighbourhood of Parkdale, there was evidence the Grade 3 student had been sleeping on the floor and had been subject to poor living conditions that he did not want to discuss.

"I saw probably the worst thing I've seen in 20 years of policing," he said.

He said he'd like to hear from anyone with any information at all about the girl — teachers, neighbours, even convenience store owners.

"I don't care who they are. If they have information, no matter how insignificant it may seem, it could be important to us," Ryan said.

Legal guardian charged with second-degree murder

Katelynn's legal guardian, 29-year-old Donna Irving, has been charged with second-degree murder in connection with the girl's slaying. Ryan confirmed that Irving has been charged and convicted of violent crimes in the past.

Donna Irving, shown in a courtroom sketch, was charged and convicted of violent crimes in the past, according to Toronto police. (CBC)

According to Ryan, Irving was granted sole custody of Katelynn in January, although she has had contact with the girl since May 2007.

Court documents obtained by CBC News show Irving took final custody of Katelynn in June. The documents said that both Katelynn's mother, Bernise Sampson, and her father were drug addicts.

According to the documents, Irving said Katelynn had been living with her since May 2003.

Outside her west-end home Tuesday, Sampson said she was unaware of Irving's violent past.

"I do not know about Donna's past and I don't want to hear about no custody and what I did and what I didn't do. Everybody makes a mistake in life, there's nobody perfect. But I thought I had a friend," Sampson said.

She said Monday that she put her daughter in Irving's care while she sorted out some undisclosed personal problems. She and Irving had been friends for 10 years.

Irving has two children of her own; both are being cared for by their father.

Bernise Sampson says the system should have done a better job of protecting her daughter. (CBC)

Officials began an autopsy on Katelynn's body at 10:30 a.m. ET Tuesday, a procedure that was continuing Tuesday afternoon. Ryan said the autopsy was taking longer than expected because of the "complicated" nature of Katelynn's injuries. He would not elaborate.

He said it was too soon to say when Katelynn died, although it was clear when emergency workers found her that she had been dead for some time.

Irving called 911 early Sunday, claiming that Katelynn had stopped breathing after choking on food. Ryan said Monday that it is clear Katelynn did not choke and that she had signs of assault across her entire body.

Ryan said police obtained a warrant to search Irving's home Tuesday night but would not confirm what officers would be looking for.

Child services agencies are investigating whether they played any role in placing Katelynn in Irving's care, Ryan said.

Custody can be granted in some cases where the person has a criminal record, depending on the offence, according to an official with the Ontario Association of Children's Aid Societies.

"If we intervened in every family where there was a criminal offence, we would have no children living with parents who had had any criminal offences at all," said Virginia Rowden.

Katelynn's mother said the system had a role to play in preventing her daughter's death.

"I think the system shoulda did a better job and they didn't do it," Sampson said.