West Mercia Police cordoned off roads surrounding the Tesco Extra store at Battlefields, in Shrewsbury, which was closed around shortly after 4pm.
Firearms officers were seen in the car park of the store in Battlefield Road.
A police helicopter was involved in the search after police confirmed they had been called to reports of a man with a firearm.
The store reopened around 8.30pm after police lifted the cordon following the search.
It is believed the call was made in good faith, said West Mercia Police.
Further details on the investigation were not revealed.
Superintendent Jim Baker, of West Mercia Police, said: “We take all reports involving firearms incredibly seriously and as such armed officers were deployed to the area and a cordon put in place.
"An extensive search has been carried out by officers on the ground, the police helicopter and a fire and rescue service drone and we’re satisfied the call was made in good faith and have been able to discount the information we initially acted on.
"I’d like to thank members of the public as there was an increased police presence in the area with some disruption to local residents.
"The cordon has now been lifted however regular patrols will continue to be carried out in the area to offer reassurance to the local community.”
People took to social media this evening after armed officers arrived at the supermarket.
In a statement earlier tonight the force said: "Earlier this afternoon at around 4pm police received a report a man had been seen on the roof of Tesco Extra in Battlefield Road in Shrewsbury with what was believed to be a firearm."
"Officers, including armed officers and the police helicopter, attended and a cordon has been put in place while a search of the area is carried out."
Police also closed off the Harlescott Park and Ride next to the superstore.
Many reported seeing a helicopter over the Sundorne and Harlescott area.
A Tesco spokesman said staff were assisting police but would not comment any further.