Denver Police shut down traffic on Lincoln Street and Broadway near the state Capitol for about an hour as they investigated a backpack left near the intersection of Lincoln and East 13th Avenue Friday afternoon.

Some buildings near the abandoned bag were evacuated and tenants of others were told to stay away from north facing windows as police investigated.

Denver Police spokesman Sonny Jackson said the city is mentally on high alert as a result of the bombs that were set near the finish line of the Boston Marathon on Monday and the events that have followed.

“We are simply being cautious,” Jackson said shortly after the pack was picked up and caution tape strung along 13th between Lincoln and Broadway was removed.

The abandoned backpack was reported at about 12:30 p.m.

Tyler Rheem, who works in the Alps building near where the pack was left, said he stepped out of his building around 12:50 p.m. Within minutes, he received e-mails from the building manager advising tenants first that buildings along 13th were being evacuated, and later, advising occupants of north facing offices to stay away from their windows.