At least seven people, including a gunman, have died in a shooting at a Sikh temple in Oak Creek, Wisconsin, police says.
A police officer had been shot multiple times but was expected to survive, Greenfield Police Chief Bradley Wentlandt.
He said a “civilian” was also being treated for gunshot wounds.
Police cannot confirm reports that more gunmen are inside the building.
They say the situation remains “very fluid”.
Chief Bradley Wentlandt said that multiple calls had been made to the 911 emergency services number at about 10:25 local time.
He said a police officer had been sent to the scene and had “engaged an active shooter”, during which he had been shot multiple times.
Police have corralled journalists outside the temple and urged them not to broadcast aerial footage that could compromise the operation.
Oak Creek is a town of about 30,000 people in the south-east corner of the state.
Chief Bradley Wentlandt said police had identified four people dead inside the temple and three outside, including the gunman shot by police.
But he cautioned that he was giving the “best information we have now – it may change”.
He said security services were trying to co-ordinate the response and secure the scene, and said another briefing would be held at 15:30 local time.
Parminder Kaleka, who was waiting outside the temple, told the Milwaukee-Wisconsin Journal Sentinel that she had phoned her brother-in-law – who she said was the priest of the temple – who was inside “at that time [the] shooting happened”.
“He told me 25 or more people got shot, at that time they don’t even know if they are dead or alive, so a lot of people got injured.”
She said she had heard her brother-in-law had also been shot, and said desperate families were gathered outside the temple waiting for news.
“This is a big tragedy for our church,” she said, saying everyone had always assumed it would be a place of safety.
Other relatives of people inside the temple at the time of the shooting said they had heard reports of children being held hostage inside the basement, but there has been no confirmation of this.