Police in Philadelphia found explosives and other suspicious materials in a van on Wednesday night, multiple reports said, while authorities imposed a citywide after-dark curfew to quell the violence and looting that erupted following a police-involved shooting.
A bomb squad was called out to the scene, with no injuries reported, according to NBC10.
Philadelphia city officials imposed a curfew to quell the outbreak of looting and violence that marred peaceful protests over Monday's shooting death of Walter Wallace, who was wielding a knife and behaving erratically when shot by police.
Family members of the deceased man said he suffered from mental problems and was undergoing a nervous breakdown when police confronted him.
Wallace's death sparked two nights of rioting and skirmishes between police and protesters, with earlier reports of around 50 officers injured and 172 people arrested.
Calm largely prevailed on Wednesday after Mayor Jim Kenney imposed a curfew, with a protest rally planned for the evening called off, and four people arrested for curfew violations.
"Seeing police spread throughout the city, most near retail businesses. Hearing reports of smaller-scale looting but nothing like the scene from last night near Walmart," he wrote in a tweet.
On Tuesday, rallies began peacefully but grew confrontational as darkness fell, with clashes between police and demonstrators and some looting of stores.
Tension has gripped the city since the Oct. 26 deadly police shooting of Wallace, whose father, Walter Wallace Sr., later appealed to people to "stop the violence" out of respect for his son and family.
"I don't condone no violence, tearing up the city, looting of the stores, and all this chaos," he told reporters and a gathering of people. "It's an SOS to help, not to hurt."
Wallace suffered from bipolar disorder, and his psychological difficulties were relayed by his wife to the officers who encountered him before the shooting, a lawyer for his family said.
John McNesby, president of the Fraternal Order of Police Lodge No. 5, defended the officers.
"These officers were aggressively approached by a man wielding a knife," he said in a statement.
Several hundred guardsmen are slated to be deployed within the next 24 to 48 hours, confirmed Lt. Col. Keith Hickox, a spokesperson for the Pennsylvania National Guard.
Philadelphia District Attorney Larry Krasner said in a statement that an investigation into Wallace's shooting is underway.