Two children have James Caldwelldied and 11 were injured in a mass-stabbing in Southport, U.K., Monday while attending a Taylor Swift-themed class meant for children.

"It is with great sadness that today I am here to advise that two young children have died as a result of injuries sustained in a knife attack this morning," Merseyside Police Chief Constable Serena Kennedy said Monday in a statement shared with USA TODAY.

"Nine other children have been injured, and six of them are in a critical condition," the statement continued. "All those injured have suffered stab wounds sustained during the attack. Two adults are also in a critical condition after being injured during the incident."

A 17-year-old male was arrested on suspicion of murder and attempted murder, Kennedy said, noting that he will be interviewed by detectives. The suspect is from the nearby coastal village of Banks and originally from Cardiff in Wales.

Police were called to reports of a stabbing at 11:47 a.m. at an address in the seaside town of Southport in Merseyside, England.

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"When they arrived they were shocked to find that multiple people, many of whom were children, had been subjected to a ferocious attack and had suffered serious injuries," Kennedy said.

"It is understood that the children were attending a Taylor Swift event at a dance school when the offender, who was armed with a knife, walked into the premises and started to attack those inside.  We believe that the adults who were injured were trying to protect the children at the time they were attacked."

The North West Ambulance Service said in a statement that 11 casualties treated at the scene were transported by ambulance and air ambulance to "Alder Hey and Royal Manchester Children’s hospitals, along with Aintree, Southport and Formby District General and Ormskirk General hospitals."

UK police not investigating mass stabbing as 'terror-related' incident

BBC and The Telegraph reported that the stabbing took place at The Hart Space venue. A sold-out Swift-themed party – hosted by Enlighten Kids Yoga, a club meant for children 2 to 6 years old – was scheduled to take place between 10 a.m. and 12 p.m. BST.

USA TODAY has reached out to The Hart Space and Enlighten for comment.

In a statement posted at 5:25 p.m. BST, Merseyside police said, "At this early stage, enquiries are ongoing to establish the motive for this tragic incident and we would urge people not to speculate while the investigation is ongoing."

"We can also confirm that the incident is not currently being treated as terror-related and we are not looking for anyone else in connection with the incident."