Firstly, two men arrested on Wednesday suspected of having blown up bus shelters are now being heard about the explosion at the school. Secondly, a new lead, which showed up on Friday, is now being investigated, and points to one or several other suspects.

“We’re looking into that more carefully, and we’ll see what we discover today,” said Christer Nilsson, operative manager at Söderortspolisen, southern Stockholm’s police force, to news agency TT.

The object behind the explosion at Solbacken preschool was a powerful home-made firecracker, reported the police on Friday.

A four year-old girl injured her hands in the blast, and was taken to the hospital, where she was operated upon for several hours. The girl was still in hospital on Friday, but under the circumstances felt reasonably well.

According to police reports, it is believed that she will make a complete recovery.

“The girl found the cracker inside the preschool’s area. It exploded in her hand,” said the Stockholm police force’s Lennart Löfgren to newspaper Dagens Nyheter.

The firecracker was lodged in the gutter of a shed in the preschool’s yard. When the girl pulled on the cracker, she heard a hissing noise before it exploded.

The incident has caused great concern among parents in the area, and employees at the preschool were shaken.

“We were very shocked, and feel strong empathy with the girl and her family,” said Lena Rabe, deputy district director of Farsta, to Dagens Nyheter.

“We’re responsible for looking over the yard, to ensure that there isn’t any glass, cans or anything of the like, and this is done daily,” explained Rabe, who didn’t want to comment on whether the preschool’s employees ought to have found the cracker in the gutter.

On Friday police searched through several other preschools in the area for more firecrackers.

“I’m worried there are more crackers deployed,” said Therese Biller, a concerned parent living in the area.