BELLEVUE, Wash. -- A Bellevue office building that burned for hours after erupting in flames late Wednesday afternoon is still too unstable for fire investigators to go inside.

The fire broke out shortly after 5 p.m., disrupting rush-hour traffic on Interstate 90 and Interstate 405 with huge plumes of smoke blackening the sky for miles.

The fire damaged much of the McCarthy building that housed several companies including software, financial and engineering firms that employed hundreds of people.

SLIDESHOW: Flames Shoot Through Roof Of Bellevue Building

Millions of dollars in equipment alone were estimated to have been lost in the fire.

Many workers were still inside the building when the fire broke out, but the building's smoke alarms did not go off. Employees ran through the building to make sure everyone got out safely.

A few smoldering hot spots were still visible Thursday morning and firefighters said they were concerned about the building's stability. The charred frame of the building will have to be shored up before investigators can go inside and look for the cause.

The building was not equipped with a sprinkler system.

No one was hurt.