The alarm came shortly after 12:30 pm on Wednesday. The woman was seriously injured, but she was conscious when she was taken to hospital by ambulance helicopter. Her condition is considered stable, the police announced in the evening.
The municipality states that the woman is a 30-year-old teacher.
It's one of the staff who was stabbed in the schoolyard, said the school's principal earlier and added that the students were indoors in the school building.
In the afternoon, one person was arrested, but was later released in the evening after a decision by the prosecutor.
The search for a perpetrator is still ongoing, according to the police on their website.
Children can leave school
After the cordons were lifted, the children who had been indoors in the school could start being picked up by parents and leave the premises, from around 4:30 pm.
The crisis support group (which provides support in special crisis situations) is currently opening up a nearby recreational center for those who want to come and get support, says Mats Johansson, safety manager in Upplands Väsby municipality, to TT.
The affected school has students from preschool to 9th grade. Earlier on Wednesday, the police announced that there was no danger for the students who remained in the school.
Large deployment
A large number of ambulances and police cars with flashing blue lights were on the scene, reports TT's correspondent, and many parents had gathered outside the police cordons. Some waved to their children who were looking out through the school's windows.
Among those who gathered outside the school was the 15-year-old student Tobias Holmertz, who left school during lunch.
We came up from Hemköp and saw a lot of police cars. Is something happening at the school? we joked, and then suddenly there were more and more police cars and ambulances and a helicopter above us, he said.
I'm shocked.
"Feels terrible"
Parent Jenny, who does not want to give her last name, was one of those waiting at the cordons, and she has a son at the school.
I've talked to him, so I know he's safe, she said on Wednesday afternoon and continued:
You read and hear so much about this kind of thing happening in society, and then it comes so close. It feels terrible.
Another person was taken to hospital, according to the police, due to shock.
A preliminary investigation into attempted murder has been initiated.
