Employees from about a dozen businesses had to be evacuated today from the six-story former Maine National Bank building in Portland after workers doing renovations on the fourth floor accidentally activated the sprinkler system and sent water cascading to the floors below, according to Portland fire officials.

Deputy Fire Chief Steve Smith said power was shut off to the office building, located at the corner of Exchange and Congress streets, so workers were sent home. He said power wasn’t expected to be restored until tomorrow.

The event occurred shortly after 11 a.m. and a part of Congress Street was blocked off for more than an hour as emergency vehicles responded to the scene.

Smith said there are actually three distinct parts of the building and only the 120 Exchange St. side of the building was impacted. He did not know the names of the businesses involved but said one was a computer-training company located below where the sprinklers were set off. Smith said he expects that company may have significant business losses because some of its computers were damaged by the water.

The fifth and sixth floors were not damaged but were evacuated as a precaution when the power was turned off, Smith said. He said no one was in danger during the incident.