Three people in total were injured when a substance was thrown at students and a staff member on Monday afternoon.

“Tests of the substance are ongoing. At this stage officers believe it to be acidic,” London police said in a statement, which noted a 14-year-old girl’s injuries “may potentially be life-changing”.

“Urgent enquiries are underway to identify and arrest those responsible.”

A 16-year-old boy, whose injuries were not life-changing, was also in hospital, after the incident at the Westminster Academy school.

The third victim, a woman aged 27, was discharged from hospital after suffering injuries not said to be life-changing.

The UK has battled back against attacks involving corrosive substances such as acid after they spiked in the middle of the last decade and saw incidents decline until a resurgence in 2022.

The attacks returned to the spotlight this year after an attack on a woman and her two young daughters in London.

Teenage violence in the British capital, especially knife crime and shootings, has also been a persistent problem.

In July, a 15-year-old boy was found fatally shot in a park near the scene of Monday’s incident.

The Westminster Academy site was closed on Tuesday.

A statement on its website, which did not mention the attack, said students were learning online.

In its statement, police said “a number of crime scenes” were in place.

The force said various emergency services had responded after police were alerted on Monday afternoon. Two officers were taken to hospital as a precaution after they reported feeling unwell, it added.