The Los Angeles Police Department evacuated its Rampart Area station Tuesday after an envelope containing an unknown powder was found at the station.

The envelope contained a threat directed at one of the officers involved in the fatal shooting of a Guatemalan immigrant earlier this month in the Westlake District, according to sources familiar with the incident who asked not to be identified because the investigation is ongoing. The nature of the threat was not specified.

[Updated at 2:34 p.m.: Officials said they determined the white powder was not hazardous.]

Nearly a dozen people may have been exposed to the powder around 1 p.m. at the station at 1401 S. 6th Street, according to police officials.

Manuel Jamines was shot and killed Sept. 5 at the corner of 6th and Union Avenue after police said he advanced on officers with a knife.

The LAPD said that Jamines was threatening people before the fatal confrontation. Residents and the LAPD agree that Jamines was intoxicated at the time of the shooting and witnesses said he had a knife. Another witness has questioned that account and whether the man represented an imminent threat to the officers.

The shooting led to protests, the largest of which took place days after the incident when about 300 protesters gathered at the LAPD's Rampart Station, some hurling eggs at police cars and others throwing objects at station windows.

Los Angeles city prosecutors have said they expect to charge more than a dozen people in the series of street protests in the Westlake district related to the shooting.