BALTIMORE (REUTERS) - A grand jury has brought charges against six Baltimore police officers in the death of Freddie Gray from injuries suffered while in police custody, Baltimore City State Attorney Marilyn Mosby told a news conference on Thursday.

Gray's death on April 19 set off weeks of largely peaceful protests in Baltimore punctuated by a day of rioting and arson after his funeral on April 27, when rioters threw rocks at police and set buildings and cars on fire.

The grand jury's findings, including one count of second-degree depraved heart murder against officer Caesar Goodson Jr, were largely in line with the charges that Mosby announced early this month.

The officers will be arraigned on July 2.

"These past two weeks, my team has been presenting evidence to a grand jury that just today returned indictments against all six officers," Mosby told reporters.

She took no questions.

The death of Gray, 25, followed a string of police-involved deaths of unarmed black men in Ferguson, Missouri, New York City and North Charleston, South Carolina, which provoked waves of protests across the United States.

The grand jury also charged Goodson, police officers William Porter, Edward Nero and Garret Miller, Lieutenant Brian Rice and Sergeant Alicia White with reckless endangerment.

The grand jury did not bring charges of false imprisonment against Rice and Nero, charges that Mosby had pursued.

The Fraternal Order of Police union, which represents the officers, did not immediately respond to a request for comment.

The US Bureau of Alcohol, Tobacco, Firearms and Explosives released photos on Thursday of several people suspected of setting fires during the April 27 rioting.

They included a man suspected of torching a CVS pharmacy, where arson and looting became a symbol of the unrest.

Authorities are offering US$10,000 (S$13,000) rewards in the cases.

The ATF has investigated the torching of six stores and a seniors' centre under construction, it said in a statement.

The Baltimore Fire Department has said 61 structural fires were recorded over April 27 and 28.

In addition, 144 vehicles were set on fire, Mayor Stephanie Rawlings-Blake's office has said.

In a Reuters/Ipsos poll taken after the protests in Baltimore, 69 per cent of respondents said America had a serious issue with race.

Nearly three-quarters said there was more racism in the United States than the country was willing to admit.