A man is in custody today after being arrested yesterday in connection with the double murder in Leytonstone last Saturday.
Aaron Carriere, 21, and Josiah Manful, 20, were found stabbed to death in a black Ford Fiesta in Montague Road at 1am on March 1.
Police re-visited the crime scene in the early hours of yesterday morning and arrested a 19-year-old man.
It is understood the pair were attacked last weekend by a gang wielding knives and baseball bats.
Both men were pronounced dead at the scene by paramedics.
A post-mortem examination revealed Mr Carriere died of stab wounds to the neck, while Mr Manful died from shock, haemorrhaging and stab wounds to the chest.
In total, 12 people have been arrested in connection with the fatal stabbings.
Eleven suspects including a 49 year-old woman suspected of assisting an offender have been bailed pending further enquiries.
An incident room has been opened in Barking under Detective Chief Inspector Neil Attewell from the Homicide and Major Crime Command (HMCC).