A 16-year-old girl has died and two men have been arrested after suffering serious injuries in the Rhondda.
The teenager’s death in Treorchy was “sudden and unexplained” and a post-mortem examination is due, South Wales Police said.
Emergency crews were called at about midday to reports of a stabbing in Baglan Street, which is sealed off.
Police said those involved were known to each other and no one else was being sought over the matter.
The girl’s family is being supported by specially-trained officers and efforts are being made to contact other relatives.
Supt Rich Jones, said: “This is clearly a very serious incident which has caused significant shock and concern for both the local and wider community.
“We have a dedicated team of detectives working hard to establish the exact circumstances that have led to the tragic death of this young girl.”
The investigation was “still in its early stages”.
“There will be significant police presence in Baglan Street over the weekend but we will reopen the road at the earliest opportunity,” Supt Jones said.
“In the meantime, the support and understanding of the local community is very much appreciated.”
The police cordon was erected around a takeaway restaurant called Blue Sky, with a small white tent placed outside the premises.
The public has been urged by police to “refrain from speculation” about the incident.
A spokesman said: “We attended the scene with one rapid response vehicle, three emergency ambulances, our hazardous area response team and the Wales Air Ambulance.”
Rhondda MP Chris Bryant tweeted he was aware of “disturbing events on Baglan Street” and later said he understood police were not looking for anyone else in connection to the incident.
He said: “Because there have been so many emergency services turning up, people thought there must be some massive manhunt going on.
“I can reassure everyone the police are in control of the situation.”
Mr Bryant described what had happened as “a very worrying and upsetting episode”.
“You just don’t think that something like this is going to happen in the Rhondda,” he said.
“But I can reassure everyone, having spoken to the police, they are completely on top of the situation.
“They are not looking for anybody else as I understand it.”
Mr Bryant also said that primary school Ysgol Gynradd Gymraeg Ynyswen had been aware and had taken “all necessary precautions”.
First Minister Mark Drakeford said his thoughts were with “everyone in the community”.
Sarah Belgrove, 54, who lives a few doors from the scene, said the air ambulance was forced to land some way from Baglan Street.
“The helicopter was in the sky and had to land in the school, in the playground – it’s like a football field,” she said.
“The paramedics who got out of the helicopter flagged down some cars to give them a lift to the to the scene.”
Neighbour Mavis Wakeford, 79, added: “I’ve lived here all my life and nothing like this has ever happened before.”
Andrew Morgan, leader of Rhondda Cynon Taf council, tweeted his thanks to emergency services for “the significant attendance which is ongoing”.
A Wales Air Ambulance landed in Ynyswen at 13:00 GMT from Mid Wales Airport in Powys.
Police urged anyone who may have witnessed the events in Baglan Street to contact the force.