Palo Alto officials have called in a structural engineer to determine if the support columns in the building at University Avenue and Bryant Street are strong enough for the building to remain standing and whether fire inspectors can work in the building to determine the cause of the Sunday night fire.

The fire in the offices above Walgreens started at 9:35 p.m. Sunday night and burned for more than five hours. More than 50 firefighters fought the blaze.

The building may need to be strengthened before inspectors can work in it, Police Agent Rich Bullerjahn said. In a worst-case scenario, the building may have to be demolished, he added.

University Avenue and Bryant Street adjacent to the building are still closed to traffic. Bullerjahn said the city should know by early evening if the streets can be reopened.

-- Don Kazak