Britain's information watchdog is investigating a police database of potential gang members that Amnesty International alleges breaches human rights law.

Amnesty says the Metropolitan Police Gangs Matrix "is racially discriminatory, stigmatizing young black men for the type of music they listen to or their social media behavior."

The database holds information on almost 4,000 people, 78 percent of them black. Police figures show 27 percent of those prosecuted for youth violence are black.

Scotland Yard says the database, set up after England's 2011 riots, aims to "reduce gang-related violence and prevent young lives being lost" by steering young people away from gangs.

The Information Commissioner's Office said Wednesday it is "considering how the database is used and if any aspects of it constitute a breach of the Data Protection Act."