A woman found the 300 dead amphibians round the edge of her garden pond, near Llandrindod Wells, following a cold snap last month.
It is unclear why so many perished, but such a large number living in the pond could have depleted the oxygen levels.
The discovery followed the thaw of ice and snow that had been covering the pond for several weeks.
The woman, who does not want to be named, is a member of Radnorshire Wildlife Trust (RWT).
Read full story HERE.