Two male moped riders went on an acid attack spree across London, spraying a corrosive substance in victims' faces, police said.
One of the five people to be targeted on Thursday night (13 July) was left with life-changing injuries.
A 16-year-old boy has been arrested on suspicion of grievous bodily harm and robbery and is currently in custody.
The attackers first struck at around 10.25pm in east London when they pulled up alongside another moped rider in Hackney Road at the junction with Queensbridge Road.
Police say the suspects then threw a corrosive substance in the victim's face, with one stealing his moped and the other making off on the moped they arrived on.
Pictures posted on social media showed takeaway delivery drivers trying to help the injured man.
Witness Sarah Cobbold wrote on Twitter: "Police and ambulances on Hackney/Queensbridge Road, possible acid/petrol attack. Lots of @UberEATS @Deliveroo drivers rallied round."
The 32-year-old victim was taken to an east London hospital. His injuries are not being treated as life threatening or life changing.
Just 25 minutes later, at around 10.50pm, another man had a corrosive substance thrown in his face by two males on a moped in Islington's Upper Street, at the junction with Highbury Corner.
He was taken to a north London hospital where police are awaiting an update on his condition.
A third victim was targeted 15 minutes later in Shoreditch High Street, where a man reported having a corrosive substance thrown in his face by two males on a moped.
The victim was taken to hospital and his injuries are not believed life threatening or life changing.
Just 10 minutes later, at 11.18pm, police received a call at a robbery in Cazenove Road, Stoke Newington. Officers arrived to find a male acid attack victim in his mid-20s.
He suffered facial injuries described by police as "life changing".
A fifth suspected acid attack was then reported to police at 11:37pm in Chatsworth Road, Lower Clapton.
A man said he had been on his moped in traffic when two males on another moped pulled up alongside him and sprayed liquid in his face. They stole his moped and made off.
The victim made his way to his home address before contacting police. He was taken to an east London hospital. His injuries are not life threatening and not life changing.
All five incidents are being treated as linked, police said.
Detectives have appealed for anyone with information to come forward.
Any witnesses, anyone with information or in possession of footage of these incidents should contact police on 101 or tweet @MetCC. To remain anonymous you can call Crimestoppers on 0800 555 111.