Four people have been “sprayed with an unknown substance” at the University of Greenwich campus.
Police were called to the university on Avery Hill Road shortly after midnight to reports of a man being attacked and sprayed with the unidentified liquid.
The emergency services found a man with head injuries before police found three other people who had also been sprayed with the non-toxic substance.
None of the victims are believed to have suffered life-changing or threatening injuries.
The Met Police said no arrests have been made and urgent enquiries are ongoing. A crime scene remains in place.
A spokesman for the university added: “Following a police incident in front of our Avery Hill campus overnight, the main entrance is currently closed, although the rest of the campus is open as usual.
“Staff, students and visitors will be directed to an alternative entrance by stewards on arriving at the campus.
“There may be some delays to the campus bus service as a result.
“We will keep you updated this morning to advise when the main entrance is reopened.”
A Metropolitan Police spokesman said: “On Tuesday, police were called to Avery Hill Road following reports that a man had been attacked and sprayed with an unknown substance.
“Officers attended the scene alongside the London Ambulance Service who treated a man for head injuries on scene before taking him to hospital.
“Whilst conducting enquiries on scene, officers found that three other people were sprayed with the substance.
“Tests were carried out and it was found that the substance was non-toxic. None of the victims suffered any life-changing/threatening injuries.
“At this early stage, there have been no arrests and urgent enquiries are on-going. A crime scene remains in place.”