A man was taken to hospital after being stabbed in the stomach on Saturday night, while a woman was also injured in the attack.
Police and ambulance crews were called to a property in Meadow Road, Rush Green at 10.40pm after reports of a disturbance.
They found a 39-year-old man suffering from a stab wound and a woman suffering minor facial injuries.
Officers believe that three suspects, all described as white males in their early 30s, attended the address, with one of them forcing their way in and assaulting the victims.
The woman did not require hospital treatment but the man was taken to an east London hospital. His injuries were said to be not life-threatening.
Detectives from Havering are leading the investigation into the incident and urge anyone with information to call 101.
There have been no arrests.
Meadow Road was cordoned off for the night following the incident.
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