Police in west London say that an acidic liquid was thrown at students and staff at a school, leaving a teenage girl with potentially fatal injuries.

Staff members at Westminster Academy, located at 442 Alfred Road, alerted patrolling officers to the presence of a drug at 4:42 p.m. on Monday.

A statement on the academy website on Tuesday says the school is closed.

Officers who responded with paramedics and the London fire brigade found three people injured, including a 14-year-old girl “whose injuries may potentially be life-changing” and who remains in hospital, police have said.

A 16-year-old boy, whose injuries are not life-threatening or life-changing, also remains in hospital, while a 27-year-old woman has been discharged from hospital.

Two officers were taken to hospital as a precaution after they reported feeling unwell.

“Tests of the substance are ongoing,” the Metropolitan police said. “At this stage officers believe it to be acidic. Urgent inquiries are under way to identify and arrest those responsible. A number of crime scenes are in place.”

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.