Elinor Syversen, 47, was alerted to the snake when her colleague started screaming as she caught sight of it inside the fruit container they were both unpacking.
"I didn't believe it at first," Syversen told The Local.
"It was brown and 45 to 50cm long. I was a little bit shocked."
The pair believed the animal was unconscious but were nevertheless concerned. The powerful species, which can grow to up to 3 metres in length, squeezes its prey to death before swallowing it whole in the wild.
Syversen bravely used a broom to put it inside another box, which the team left in a cold outdoor store room in an attempt to prevent the animal waking up when it got warmer. Boa constrictors are usually found in tropical climates such as in Central and South America.
The discovery was made on Tuesday afternoon, with a local vet called to the premises during the evening to take a look at the animal and snap photos of the incredible find. By then it was clear that the snake was dead.
A fully grown boa constrictor. Photo: AP/Seth Wenig
The supermarket, which is part of the nationwide Ica chain, was continuing to store the reptile on Wednesday. Syversen, who was enjoying her day off, told The The Local she was expecting a phone call to advise her what to do next. She has already emailed the code on the box to managers, which should help them to trace where the bananas and the snake came from.
"I just want to get rid of it. I have two kids and a partner and my partner is very afraid of snakes!" laughed Syversen.
However she said that she was planning on taking her children to the store to show them the boa constrictor.
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"The boy is four and he really wants to look at it!"
The Local has approached Ica for a comment.
According to regional newspaper nwt.com, which first reported the story, The Natural History Museum in Gothenburg is considering giving the dead snake a new home.