Ferguson unrest: Police 'used tear gas on peaceful protesters'
19 August 2014 Last updated at 10:02 BST
The US attorney general is to travel to the riot-hit town of Ferguson, as the federal authorities step up efforts to restore calm after the fatal police shooting of an unarmed black teenager.
Eric Holder will go to the town on Wednesday to meet officials in charge of a federal investigation into the killing of Michael Brown on 9 August.
President Barack Obama urged the local community to "try to unite".
Professor Stefan Bradley of St Louis University witnessed a police stand-off with protesters overnight, and described what he saw to the BBC.