A 21-year-old man has been arrested following an "awful" nightclub acid attack that left two people partially blinded, police said.
The man was arrested at an address in north London on suspicion of grievous bodily harm, the Metropolitan Police said.
He was one of three men being sought, including the boyfriend of reality television star Ferne McCann, after a corrosive liquid was sprayed during an argument at Mangle in Dalston, east London.
A 22-year-old woman and a 24-year-old man were both blinded in one eye in the attack in the early hours of Monday, which has left "many others" requiring long-term treatment, the force said.
It came as police carried out three arrest warrants at addresses in Hertfordshire and others in Milton Keynes.
They are appealing for the public's help in locating Arthur Collins, the 25-year-old boyfriend of reality television personality McCann, who issued a public plea for him to turn himself in, and another man.
Detective Inspector Lee McCullough said the net was "closing in on those we believe to be responsible".
He said: "This incident has caused suffering to a large group of people and left a young man and a woman blinded in one eye and many others needing long-term treatment.
"The noxious substance used has not yet been confirmed, but samples retrieved from the scene have been sent for analysis. If you were there and saw anyone involved inside or leaving the nightclub, please get in touch."
He called the attack "awful" and warned that "anyone found harbouring those wanted for questioning by police can expect a knock at the door and could well find themselves under arrest".
The 24-year-old victim blinded in one eye and another man, 29, have been transferred to a specialist burns hospital in Essex, where they remain in a serious but stable condition.
Officers believe a dispute between two groups of people developed inside the venue, resulting in a noxious substance - which police believe is acidic - being sprayed by a male suspect directly at the pair.
Some 20 people suffered burns, with 12 people attending hospital, including a 22-year-old woman who suffered injuries to her face and has been left blinded in her left eye.
Other people inside the venue suffered the effects of the substance.
A 33-year-old woman, who was arrested on suspicion of firearms offences following the raids on Thursday, has been bailed to return at a later date.