Up to 5,000 pigs are believed to have been killed by a single fire that raged for three hours in Sweden on Sunday morning.

Police and fire services were called to the sty in Kalmar at around 3.30am, but arrived to find several central buildings already engulfed in flames.

No people were harmed in the fire, which was brought under control and extinguished during the morning, but police said thousands of animals were feared dead.

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“There is concern that some 3,000 pigs have died in the flames. That is the information I have received from the police officers at the scene,” police spokesperson Mikael Erkki was quoting as saying in the Swedish edition of The Local.

That estimate was later revised up to 5,000, police said, but the final tally will have to be confirmed by veterinarians when they inspect the site in due course.

Kalmar emergency services spokesperson Juha Vierola said: “The fire is out now. Not all the buildings burned down, the fire was contained in the central buildings on the farm.”

Police told reporters they do not currently suspect arson, though the cause of the fire remains unknown.