Flowers have been left outside the building where Lola lived in the 19th arrondissement

Parisians have been stunned by the shocking murder of a 12-year-old schoolgirl whose body was found on Friday in a container in the courtyard of her apartment building.

The girl, named Lola, had spent the day normally at school, but her father raised the alert when she failed to return home in the afternoon.

Later in the evening the presence of a transparent plastic packing box was reported at the foot of the apartment building - a residential block in the 19th arrondissement where Lola's father is employed as a concierge.

Lola's body was found squashed inside the container, hidden by a covering of material. Her hands and feet were tied and she was reported to have a gash on her neck, though the autopsy this weekend found she had died of asphyxiation. Two Post-it notes were also on her feet, one saying "0" and the other "1".

Early on Saturday police arrested the main suspect in the killing - a 24-year-old Algerian-born woman named in the press as Dahbia B.

The woman was identifiable on a security video taken at the apartment building, in which she was seen entering the main door on Friday afternoon in the company of Lola.

Later she was seen leaving the building pulling a container and then acting incoherently on the street. One eyewitness said she asked for help in return for money from an "organ-trafficking affair".

However, police said they did not believe this was a serious lead. Their most plausible theory is that Dahbia B, who has no fixed abode, is psychologically unstable and that her act was "gratuitous".

Also in custody is a 43-year-old man who is believed to have ferried Dahbia B and the container in his car. Police think that, having been driven by him around the Paris suburbs, Dahbia B returned to the apartment building - where her sister also is a resident.

There the two sisters are reported to have had a noisy row, before Dahbia B left again - this time without the container. She spent the night in a flat in the suburb of Bois-Colombes where she was picked up the next day.

'We can't trust anyone'

Police have opened an investigation for murder of a person under 15 years of age accompanied by acts of torture and barbarity. Dahbia B is expected to be placed under judicial investigation and kept in custody.

At Lola's school, children and parents were visibly distressed on Monday morning. The school received visits by Education Minister Pap Ndiaye and Paris Mayor Anne Hidalgo, and psychological support teams have been sent to comfort pupils.

"My daughter cried all weekend, she hasn't slept a wink," Gasmi, a father of two, told Le Parisien newspaper. "We can't trust anyone now in our neighbourhood. I am very afraid for my children."

"It's turned me upside-down," a local woman told the paper. "This morning I followed my son on the way to school, just a few metres behind him. Just to be safe.

"I'll take him to school from now on and I'll go and get him too. If he finishes at half past four, I'll leave work at four. Its non-negotiable."

Brigitte Macron, wife of the president, said it was an "absolutely abominable and intolerable tragedy".

-- Courtesy of BBC News