Detectives investigating two separate acid attacks, including one which has left a man critically injured, are continuing to appeal for witnesses.
Officers have made two arrests in connection with the incident in Walthamstow.
A 14-year-old boy [A] who was arrested on Friday, 3 November on suspicion of causing grievous bodily harm has been released under investigation.
A 16-year-old boy [B] who was arrested late on Saturday, 4 November on suspicion of causing grievous bodily harm has also been released under investigation.
The investigation by detectives from Waltham Forest CID into both incidents continues.
At about 18:00hrs on Thursday, 2 November on Walpole Road, Walthamstow, a fast food delivery driver, was approached by two men on a scooter as he delivered a pizza to an address.
They demanded he hand over his keys, and when he refused a struggle followed, before the suspects produced a corrosive substance and sprayed him in the face. The victim, a 32-year-old man, was wearing a helmet with the visor was up and received substantial injuries to his eyes and face.
The suspects left on their moped, leaving his behind. One wore a white helmet and one a black one.
Officers attended along with the London Ambulance Service and the London Fire Brigade.
The victim was treated at the scene with water and taken to an east London hospital.
He remains in hospital in a critical condition after inhaling the substance, and may lose the sight in both eyes.
Police are continuing to appeal for information.
Detective Chief Inspector Gordon Henderson, of Waltham Forest CID, said: "This attack has left a man fighting for his life and with terrible eye injuries. This was an innocent man going about his work as a delivery driver, who may never see again. This is not a time to hesitate, if you have any information about this crime I would appeal that you immediately call police. Your phone call could save some other innocent person; it is imperative that we arrest those responsible."
Detectives are also investigating a second incident in which a corrosive incident was used a short time after the Walthamstow attack.
At about 18:30hrs, on Yarmouth Crescent in Tottenham, a second man was also attacked with a corrosive substance.
This man - also a 32-year-old delivery driver - was approached by two men on a scooter who attempted to steal his moped.
A corrosive substance was thrown in his face, before the suspects left the scene on their moped.
This man was also treated in hospital, but his injuries are not believed to be life-threatening or life-changing.
It has not been established whether the two incidents are linked, but it is an active line of inquiry and detectives in Tottenham and Waltham Forest are liaising closely.
Anyone with information about either attack is asked to contact police on 101 or contact via Twitter on @MetCC.
If you do not want to give your name, you can contact Crimestoppers 0800 555 111 or give information online at crimestoppers-uk.org.