Six children have been taken to hospital after a “serious incident” at a house in Sheffield, police said.
Officers were called to “reports of concerns for safety” at a home in Gregg House Road, Shiregreen, at 07:30 BST.
Two people have been arrested and forensics officers were seen going into the semi-detached house.
Roads have been cordoned off. An air ambulance earlier landed in the playground of Hartley Brook Primary Academy, which backs on to the road.
The school is not believed to have been involved in the incident.
No further details are yet available but police are due to give an update from the scene later.
Some residents told the Sheffield Star newspaper they thought there had been a shooting, but police said this was not the case.
South Yorkshire Police set up a cordon around Gregg House Road, with buses being diverted from the area.
Aaron Brunskill, who lives locally, said residents came out into the street at 08:00 to find about 15 police cars and four ambulances.
He said: “I know there’s children there, I’ve just seen them walking back to the shops and that’s all I know.
“Everyone speaking on the road said the first one out had to be resuscitated.”
The force said it was no longer a “live incident”.
A spokesperson said: “There will be a significant police presence at the scene throughout the day as officers continue inquiries.”
At the scene
Phil Bodmer, reporter, BBC Look North
There’s a number of police vehicles and police officers standing outside a semi-detached house.
It’s adjacent to Hartley Brook Primary Academy school, where an air ambulance landed this morning.
We’ve spoken to people who live in the area who told us there was an awful lot of police activity this morning.
Emergency vehicles – including four ambulances – were seen near to the school.
As far as we know the school is currently still open, with detectives busy doing door-to-door inquiries around the neighbourhood.