A 14-year-old girl has been left with potentially life-changing injuries, while a 16-year-old boy is in hospital, after a substance – believed to be acidic – was thrown at them by a male who approached them on the street outside their school, police have said. Officers are hunting a male suspect who they believe rode to and from the scene at Westminster academy in west London on an e-scooter, and covered his face as he launched his attack on Monday afternoon. Detectives have appealed for witnesses to come forward. “From our inquiries so far, we believe the two young victims were on Alfred Road when they were approached by a lone suspect who threw a substance at them before fleeing down Harrow Road,” said DCI Dean Purvis, who is leading the investigation. The suspect was described as a “tall, slim, black male, wearing dark clothing with his face obscured, possibly by a mask or balaclava”. Puvis added: “A member of staff bravely and selflessly rushed to provide first aid to the two victims, sustaining injuries herself in the process.” The 27-year-old woman has since been discharged from hospital. “The two teenage victims – a girl and a boy – remain in hospital. For the 14-year-old girl, we might not know for some time how severe her injuries are. But, at this time, they are being treated as life-changing.” On Tuesday, a lone police officer was guarding the entrance of the school, which is closed for the day. One local shopworker, who did not want to be named, said he heard sirens and a “big kerfuffle” outside in the aftermath of the incident. “This school, they usually have everything under control – you don’t see fights outside,” he said. “I have never seen anything like this. Yesterday was just out of the blue.”The school’s principal, Numera Anwar, said: “This was a distressing incident which took place after school hours when students and staff were leaving the school site. We are offering support to families and relatives of all involved. “This is a difficult time for our community and I took the decision to close the school today to allow for a thorough investigation and to ensure the school can resume normally from tomorrow with all safety measures in place.” Police said officers on patrol nearby were flagged down shortly before 5pm on Monday. Two were taken to hospital as a precaution after they reported feeling unwell, with each having since been discharged from hospital. They added: “Tests of the substance are ongoing. At this stage officers believe it to be acidic. There have been no arrests at this time and a number of crime scenes are in place.” Adam Hug, the leader of Westminster city council, said: “This is a truly shocking attack on school pupils and a member of staff. “The council has been in touch with Westminster academy and we will provide educational psychologists and any other support to help children through what is a traumatic ordeal. Our thoughts are with all those who have been affected. “Clearly this attack will be unsettling for the whole academy and the wider community, and we will be working with police to provide reassurance and whatever support we can. We would urge anyone with information about what has happened to contact the police.” The police said anyone who witnessed the incident, or who had information that could help should call 101 with the ref CAD 4987/30 Sept. To remain anonymous, contact the independent charity Crimestoppers on 0800 555 111.