An American woman was killed and five other people were injured in a stabbing attack in London Wednesday night, police said Thursday.
Police arrested a 19-year-old Norwegian citizen of Somali origin on suspicion of murder after the incident in Russell Square, a busy area near the world-famous British Museum.
Authorities said early indications suggested mental health was a "significant factor" in the attack. While police had initially said that "terrorism remains one line of inquiry," an updated statement said only that investigators were keeping "an open mind regarding the motive."
There were increased numbers of armed police patrolling London streets Thursday morning. The vast majority of British police do not carry guns.