The US Justice Department announced Thursday it was opening a civil rights investigation into the Missouri police department involved in the racially charged shooting of an unarmed black teenager.

The US Justice Department announced Thursday it was opening a civil rights investigation into the Missouri police department involved in the racially charged shooting of an unarmed black teenager.

The death of 18-year-old Michael Brown has already given rise to a separate federal investigation into whether Darren Wilson, the police officer who shot him, violated the teenager's civil rights.

But Attorney General Eric Holder told reporters that the Department of Justice had also determined there was cause to investigate "whether Ferguson Police officials have engaged in a pattern or practice of violations of the US Constitution or federal law."

Brown's shooting on August 9 and subsequent violent protests reopened a fierce national debate on race and the tactics used by police in dealing with minorities.
Holder, himself an African-American, visited Ferguson amid the protests, walking the streets and talking with community members.

"The decision to go ahead was based not only on what I heard," Holder said, but also public records and other documents involving minorities.

He added that the investigation "is not a stopgap or a short-term solution" but rather "a long-term strategy" meant to build trust, safety and accountability.