SAN FRANCISCO (CBS SF) — Streets have reopened Monday evening after the area of California and Sansome streets in downtown San Francisco was cordoned off due to a suspicious package.

While there were no specifics initially reported about the police activity, the San Francisco Department of Emergency Management issued an advisory at around 4:30 p.m. The San Francisco DEM and the San Francisco Fire Department both posted on their respective Twitter accounts that people should stay away from the area.

Avoid the area of California and Sansome Streets due to SFPD activity. https://t.co/CsYQrajYfo — San Francisco DEM (@SF_emergency) December 11, 2018

ALERTSF: Avoid the area of California and Sansome Streets due to SFPD activity. https://t.co/uYOhAPj8zA — SF Firefighters 798 (@SFFFLocal798) December 11, 2018

San Francisco police later confirmed that a suspicious package had been reported on the 300 block of Sansome Street at 3:36 p.m.

Police said one building was evacuated, while the rest of buildings on the block were told to shelter in place.

Currently, streets are being blocked while police have the bomb squad unit test the package. All foot and vehicular traffic has been stopped at California and Sansome streets, causing some major back-ups on neighboring streets.

Muni and Golden Gate Transit buses are being detoured around the intersection.

ATTN: #SFPD activity near area of Sansome and Sacramento. The 1, 10, 12, 41 may see delays and possible reroutes. — SFMTA (@sfmta_muni) December 11, 2018

As of 6:07 p.m. the scene was declared safe and traffic around the 300 block of Sansome Street was returning to normal.