The UK government has announced that the terrorism threat level will be raised after an attempted bomb attack on Liverpool Women's Hospital.
Three men, aged 21, 26 and 29, were arrested in connection with the blast on Sunday and a fourth man aged 20 was detained on Monday.
All four were released after being interviewed, Counter Terrorism Police North West said on Monday night.
UK Home Secretary Priti Patel said earlier that day that the terrorism threat level would be raised from “substantial” to “severe” after the attack, which came less than a month after the murder of politician Sir David Amess.
The threat level, which is set by the Joint Terrorism Analysis Centre, means an attack is considered “highly likely".
“There’s a live investigation taking place right now,” Ms Patel said.
“They will need the time, the space, to do the work that they are doing in terms of investigating the incident.”
Here is everything we know so far:
— The explosion happened inside a taxi outside the hospital moments before 11am on Remembrance Sunday, as the nation prepared to observe two minutes' silence.
— Emergency services were on the scene within minutes and one man, the passenger in the taxi, was killed.
— Police named Emad Al Swealmeen as the person who died and also as the suspect in the bombing.
— Al Swealmeen, 32, was an asylum seeker who came to the UK from Iraq several years ago and had converted from Islam to Christianity.
— The driver of the taxi, David Perry, was injured, though he managed to escape. He has since been released from hospital.
— He picked up the passenger in the Rutland Avenue area of Liverpool, about a 10-minute drive from the hospital, said Assistant Chief Constable Russ Jackson of the Counter-Terrorism Policing North-West.
— Officers said there was an explosion inside the car as it pulled up to the hospital.
Liverpool Women's Hospital explosion latest – in pictures
— Police have declared the event a “terrorist incident” and said its proximity to a Remembrance Sunday service in the city was a “line of inquiry”, although officers could not draw a connection “at this time”.
— Authorities say “inquiries indicate that an improvised explosive device has been manufactured” and are working under the assumption that the passenger built it in the taxi.
— Detectives are unsure what the motivation behind the attack was, the reason for the device’s “sudden explosion” or why the passenger asked to be taken to the hospital.
— Three men in their twenties were detained on Sunday in Sutcliffe Street, in the nearby Kensington area of Liverpool.
— A fourth man, aged 20, was arrested on Monday, also in the Kensington area.
— All were arrested under Section 41 of the Terrorism Act, under which officers can detain terrorism suspects without a warrant. They were released on Monday after questioning.
— Two addresses, one in Sutcliffe Street and another in Rutland Avenue, have been searched, with the second address yielding “significant items”, Mr Jackson said.
— Eight families were removed from their homes near the Rutland Avenue address and a cordon remained in place on Tuesday morning.
— UK Prime Minister Boris Johnson has praised Mr Perry for acting with “incredible presence of mind and bravery”, while Liverpool Mayor Joanne Anderson lauded his “heroic efforts”.
— The hospital said access for visitors would be restricted “until further notice” and there was an increased security and police presence at the site.