DULUTH, Minn. -- Husky Energy officials reported Friday that there is no evidence of damage to a structure that prompted a precautionary evacuation at the company's Superior refinery after a "pop" sound was reported Thursday.

Gas and electric power were shut off and a nearby public road was blocked after the sound was heard and defects were noted in the tower on the refinery's south side, the Superior Police Department previously reported.

A Husky spokeswoman said the activity was noted on a stack associated with the fluid catalytic cracking unit, which was the site of an explosion and fire April 26, 2018, that injured 36 people and led to the evacuation of much of Superior. The refinery has been out of commission since that time while Husky undergoes a multi-year rebuilding project.

Working with Superior police, Husky officials said they used drones to do a preliminary analysis on the stack, finding no apparent damage.

"This is a tall stack that normally has some movement in the wind; however, out of an abundance of caution, we removed people from site while we confirm the integrity of the structure," spokeswoman Kim Guttormson said. "Our priority, always, is the safety of our workers and the public."

Guttormson said additional plans are being developed to further assess the situation and determine next steps.

"Workers will remain off-site while we confirm the integrity of the stack, out of an abundance of caution," she said.

The police department said there is no risk of fire, explosion, release of chemical or other dangers to the public. However, Stinson Avenue was ordered closed until further notice, as it is within the potential "fall zone." If the structure were to fall, police said, nothing nearby would create any risk to the public.

A car is turned away by police from Stinson Avenue leading to the Husky Refinery in Superior on Thursday, Feb. 20. (Tyler Schank / tschank@duluthnews.com)
A car is turned away by police from Stinson Avenue leading to the Husky Refinery in Superior on Thursday, Feb. 20. (Tyler Schank / tschank@duluthnews.com)