A second man has been arrested following an "awful" acid attack at a nightclub that left two people partially blinded, the Metropolitan Police said.
The 24-year-old was arrested at an address in north London on suspicion of grievous bodily harm.
Hours earlier, a 21-year-old was arrested on the same charge, also in north London.
It came as police carried out arrest warrants at addresses in Milton Keynes and Hertfordshire on Friday.
However police are still searching for the boyfriend of reality star Ferne McCann - who is being sought after a corrosive liquid was sprayed during an argument at Mangle in Dalston, east London in the early hours of Monday.
Two people - a 24-year-old man and a 22-year-old woman - were both blinded in one eye in the attack.
Some 20 other people suffered burns and 12 were taken to hospital, many of whom will require long-term treatment, police said.
Other people inside the venue suffered the effects of the noxious substance.
Meanwhile police have continued their appeal for the public's help in locating another man and Arthur Collins - the 25-year-old boyfriend of McCann.
Detective Inspector Lee McCullough said: "[The net is] closing in on those we believe to be responsible.
"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."
- Anyone with information about the incident should call police on 101 or Crimestoppers anonymously on 0800 555 111.