Two boys have been arrested in connection with the murder of a teenager at London's Victoria Underground station in March.
Officers investigating the murder of Sofyen Belamouadden, 15, of Acton, said the 17-year-olds were questioned and then bailed.
Sofyen died after being chased into the station and stabbed.
Eighteen boys, aged 15 to 17, and an 18-year-old girl have appeared in court charged with murder.
They were all remanded in custody.
A number of others were arrested and bailed by police.