The (Minneapolis) Star Tribune reported no one was hurt in the 1 p.m. CST incident.
Workers for a subcontractor, Frattalone, were taking down a section of one beam when another beam next to it crashed down out of sequence. The demolition work was halted until it could be determined what went wrong, the newspaper said.
A Mortenson Construction spokesman said it was possible the tear-down could resume yet this week.
Demolition of the 32-year-old stadium where the Minnesota Vikings and Twins played began last month to clear the site for a new $1 billion Vikings stadium. The Twins moved to their own Target Field in 2010.