Thousands of troops and outside police officers have been deployed to the US city of Baltimore, following violent protests linked to thedeath of a black man fatally injured in police custody.
A week-long curfew has been announced. Schools and many businesses are closed.
On Monday, hundreds of people set fires, looted stores and confronted police across the city.
City officials have been criticised for not responding more aggressively.
US President Barack Obama said on Tuesday that the riots have unfairly overshadowed the peaceful protests about police use of force.
"There is no excuse for the kind of violence we saw yesterday," Mr. Obama said. "They are not protesters. They are not making a statement. They are stealing."
Volunteers and city workers began cleaning up affected areas on Tuesday morning. Smoke still rose from buildings set alight the night before.
Officials said about 200 people were arrested and more than 100 cars were set on fire on Monday. Fifteen buildings were destroyed.
African-American Freddie Gray, 25, died on 19 April after suffering injuries to his spinal cord and spending a week in a coma. The US justice department is investigating exactly where and when his spinal injuries were sustained.
Officials have suspended six police officers who were involved in the case.
Monday's clashes began hours after Mr Gray's funeral.
Baltimore Mayor Stephanie Rawlings-Blake said it was very clear there was a difference between the "peaceful protests of those who seek justice" and the "thugs who want to incite violence".
National Guard commander Linda Singh said that up to 5,000 troops could be put on the streets.
"We will be out in massive force," she said, adding that armoured vehicles would be used, but the city would not be under martial law.
Extra police officers are also being drafted in from the Mid-Atlantic region.
Earlier, President Barack Obama said his administration would provide whatever assistance was needed.