Following the purported incident on April 24, Ysgol Dyffryn Aman in the town of Ammanford was placed under lockdown for a number of hours.
Dyfed-Powys Police subsequently confirmed that the stab wounds sustained by two teachers and a student were not life-threatening.
There are about 1,500 students between the ages of 11 and 18 enrolled in the comprehensive school in the town of Ammanford.
The school was closed the day following the event so that the authorities could conduct their investigation.
James Durbridge, the headteacher, pledged to support the well-being of everyone affected by the tragedy.
