Police are hunting two men suspected of carrying out a "harrowing" acid attack on two people in Northamptonshire.
A 23-year-old man and a 19-year-old woman were taken to hospital with minor burns after the men sprayed them with a noxious substance as they walked across a zebra crossing in Daventry.
The men, carrying a machete, pulled up alongside the victims on a moped in the early hours of Saturday morning, according to police.
Police are testing the substance used in the attack, but believe it to be acid, after the man suffered burns to his forehead and the woman to her legs.
The driver of the moped was said to be wearing grey joggers, trainers, a cream hoodie and a white helmet, while the passenger was white, with dark hair and was wearing dark clothing.
Det Chief Inspector Louise Hemingway of Northamptonshire Police called on the public to be "vigilant" and urged anyone with information to come forward.
"This was an extremely harrowing incident for the two victims who were making their way home after a night out," she said.
"We would urge people to be extremely vigilant to this type of incident which, as evidence suggests, is becoming increasingly common in this country.
"We are appealing for anyone who has information to contact us. We are particularly keen to trace a moped which was seen in London Road at 12.45am as well as in other parts of the town centre around the time of this attack."
It comes after the Home Secretary suggested acid attack convictions could soon carry life sentences.
Public concern over acid attacks has been growing following a spate of assaults across the country, including five that took place in just 90 minutes in London.
Amber Rudd warned an overhaul of current guidelines would ensure those who used noxious liquids as a weapon “feel the full force of the law”.
Anyone with information should call 101, quoting incident 53 of August 26, or Crimestoppers on 0800 555111.