Ten people were stabbed aboard a passenger train traveling to London on Saturday evening, in what Prime Minister Rishi Sunak described as an “appalling and senseless act of violence.”

The British Transport Police (BTP) said two men were arrested after armed officers boarded the train at Huntingdon Station, about 70 miles north of London, following emergency calls at 7:42 p.m. regarding multiple stabbings aboard a London King’s Cross-bound service from Doncaster.

The U.K.’s Counter Terrorism Policing unit is assisting the investigation “to establish the full circumstances and motivation for this incident,” BTP said in a statement, though authorities have so far found no indication of terrorism.

“This is a shocking incident, and first and foremost my thoughts are with those who have been injured this evening and their families,” said Chief Superintendent Chris Casey of the BTP.

Speaking at the scene Sunday morning, Superintendent John Loveless confirmed that both suspects were detained within eight minutes of the first emergency call.

“A 32-year-old man, a Black British national, and a 35-year-old man, a British national of Caribbean descent, were arrested on suspicion of attempted murder,” Loveless said. “Both were born in the U.K. and remain in custody for questioning.”

Authorities said ten victims were transported to nearby hospitals by ambulance, while another individual self-presented for treatment later that night.

“While nine were initially believed to have life-threatening injuries, four have since been discharged,” Loveless said. “Two patients remain in critical condition.”

The motive for the attack remains unclear. Loveless cautioned against speculation, noting that early evidence suggests the assault was not terror-related.

Armed police officers and forensic teams were seen combing through carriages at Huntingdon Station into the early hours of Sunday, while the London North Eastern Railway (LNER) suspended several services along the route.

Prime Minister Rishi Sunak condemned the attack on social media, calling it “an appalling incident that has shocked the nation.”

“All our thoughts are with the victims and their families,” Sunak wrote. “I want to thank the police and emergency responders for their swift and courageous action.”

Authorities said the investigation remains active and that further updates will be provided as details emerge.