Ayatollah Khamenei made the remarks after planting three saplings on the occasion of National Arbor Day on Monday.
Calling on the Iranian officials to seriously pursue the issue, Ayatollah Khamenei stressed that if it is proven that the students were poisoned, the perpetrators of the crime should be severely punished.
"There will be no amnesty for these people," the Leader emphasized.
Referring to the importance of planting saplings in preserving the environment, Ayatollah Khamenei called for planting forest trees in addition to fruit trees and said that the wood trade has a significant impact on the country's economy.
Ayatollah Khamenei, elsewhere in his remarks, called on the officials to solve the problems of the Iranian people through every economic means possible.
The 15th day of Esfand (the last month of the Iranian calendar year), which will end on March 20, is National Arbor Day also known as "National Tree Planting Day".
MP/