Two people were being held today over the murder of an 18-year-old student who died after being stabbed in the neck.
Aliza Mirza, from Ilford, east London, died on Saturday night after being found collapsed with wounds in nearby Manor Park.
Officers arrested two men aged 17 and 45 on suspicion of murder after the incident.
Another man aged 42 and two women aged 20 and 41 were also arrested on suspicion of conspiracy to murder and later bailed.
Emergency services were called to Forest View Road at around 7.40pm amid reports a woman had collapsed.
Ms Mirza was taken to Whipps Cross Hospital where she was pronounced dead.
A Scotland Yard spokesman said the arrested people were not members of the victim's family.
"We've got an open mind as to the motive," he said.
Det Ch Insp Stephen Clayman from the Homicide and Serious Crime Command said: "We believe that there would have been people in and around the Forest View Road area that we hope may have seen our victim, who is an Asian female of slim build, either on her own or with another person or persons, and we are appealing for these people to contact us.
"We are also keen to hear from anybody who may have seen or heard anything they think was suspicious or who may have seen anyone leaving the area, either on foot or in a car."
A Scotland Yard spokesman said a post-mortem examination carried out yesterday gave the cause of Ms Mirza's death as a stab wound to the neck.
Witnesses or people with any information are asked to call police on 020 8345 3775 or Crimestoppers anonymously on 0800 555 111.