Three of the UK's biggest police forces are at the core of a nationwide hunt for a man accused of a chemical attack on a mother and two young girls in south London on Wednesday.
Police have warned that Abdul Shokoor Ezedi should not be approached and anyone who sees him should call 999.
The BBC has been piecing together what is known so far.
What happened in Clapham?
The Metropolitan Police launched an investigation at 22:00 GMT on Wednesday after several people were injured by a "corrosive substance".
Initial details said a 31-year-old woman and her two young girls - aged three and eight - were seriously hurt after the substance was thrown at them on Lessar Avenue, near Clapham Common, at 19:25.
The woman is still in hospital in a critical but stable condition, while the girls' injuries are believed to be less serious.
Residents who heard a "crash" and a "cry for help" rushed to their aid and described hearing the woman scream: "I can't see. I can't see"."
One witness told the BBC they saw the suspect lift a young child over his head and throw her onto the ground like a "rag doll", adding it was like a "horror movie".
A couple also told the BBC they grabbed water from their home and tried to help.
Five Met Police officers were injured as they responded, as were four members of the public who tried to help.
Three women and a man attempted to stop the attacker as he fled the scene. He tried to leave in a car, but he collided with a parked vehicle and then ran on foot towards Clapham Common.
The Met's Cdr Jon Savell said a laboratory analysis of the substance from the attack site found it was a "very strong concentrated corrosive substance, either liquid sodium hydroxide or liquid sodium carbonate".
What do we know about the Clapham suspect?
On Thursday, police named the suspect as 35-year-old Abdul Shokoor Ezedi.
The BBC understands that Ezedi is originally from Afghanistan, and arrived in the UK by lorry in 2016, before later being granted asylum.
He is believed to live in Newcastle and to have travelled down from the North East on Wednesday.
In 2018, Ezedi was convicted of one charge of sexual assault and one of exposure.
He received a nine-week jail term suspended for two years for the sexual assault and, for the exposure, 36 weeks' imprisonment to be served consecutively, also suspended for two years.
His suspended prison sentence for the sexual offence, passed down at Newcastle Crown Court, included an unpaid work order.
Once that was complete in 2020, Ezedi was discharged from probation supervision.
Ezedi made his first unsuccessful asylum application in 2016. He later tried a second time and said he had converted to Christianity, meaning he would have been at risk if he had returned to Afghanistan.
After this second claim was refused, he appealed against the decision and a tribunal overturned it in 2020, having heard from a church witness who said he believed that Ezedi had converted to Christianity.
Detectives believe he is known to the family injured in Clapham, but said they were not yet clear on their exact relationship.
Where is the Clapham attack suspect?
When the investigation started last week, the Met Police released an image of Ezedi around 70 minutes after the attack in Clapham.
In this image, police said Ezedi was last seen inside a Tesco Express on Caledonian Road, Islington, at 20:48 - about 5.4 miles (8.7 km) away from Lessar Avenue.
He is believed to have bought a bottle of water before leaving the shop and turning right on Caledonian Road.
The image of him also showed "significant injuries" to the right side of his face.
"This makes him distinctive," Supt Gabriel Cameron said.
The police said on Sunday that the last confirmed sighting of him was now at 21:33 on Wednesday, when he exited Tower Hill Underground station.
He had changed trains at Victoria, where he arrived on the Victoria line at 21:10 and then left on the eastbound District line at 21:16.
Are the Clapham attack victims still in hospital?
So far we know 12 people in total were injured in Wednesday's attack.
The woman and her two young daughters who were at the centre of the attack remain in hospital, according to the Met Police.
Met Police Commissioner Sir Mark Rowley told BBC Radio London some of the victims' burns were "substantial".
His force said that while none of their conditions were life-threatening, the injuries to the woman and the three-year-old girl could be life-changing.
It added it may be some time before hospital staff are able to say how serious they might be.
The five responding police officers who were injured were taken hospital and later discharged.
Three women - two in their 30s and one in her 50s - were injured when they came to the aid of the family. They have also been discharged from hospital with minor burns injuries, the Met said.
A man in his 50s who also helped declined hospital treatment for minor injuries.
How will police try to track down the Clapham suspect?
Ezedi's whereabouts and movements after the sighting are still unknown.
On Thursday night there was a heightened police presence in that area. It is close to London King's Cross, the station for trains to Newcastle.
There is also an increased presence around the Byker area of Newcastle - where Ezedi is believed to live.
Officers have also asked local residents and drivers in and around Clapham to check doorbell and dash cameras to see if they captured a man fleeing the area.
The Met posted a Farsi-language version of its appeal to locate Ezedi on social media.
The former chief constable of Northumbria Police, who organised the hunt for murderer Raoul Moat in July 2010, said she had "23 different forces" working with her.
Sue Sim told BBC Radio 5 Live: "When British policing works together, there is nothing better than that for catching criminality.
"British Transport Police (BTP) will be involved, Northumbria Police... because that is where he [Ezedi] is known to live.
"There will be information sent around to all forces with officers being urged on their daily briefings to keep an eye open for this man.
"Officers will be trawling through all the CCTV in any of the stations, in the area; checking up on any relatives and friends and making sure they track this man."
Cdr Savell said he was "hugely grateful" to the public for the "significant number of calls" the force had received, as "your help is critical."
"I must warn anyone who is helping Ezedi to evade capture - if you are harbouring or assisting him then you will be arrested," he added.
A reward of up to £20,000 is also being offered to anyone who can provide any further information.