Does energy of type IIP supernovae depends on stellar mass?

We determine the oxygen density in the central zone of nine type IIP supernovae (SN~IIP) at the nebular stage using oxygen doublet [O I] 6300, 6364 \AA. Combined with two available estimates these data indicate that oxygen densities on day 300 are distributed in rather narrow range $(2.3\pm1)\times10^9$ cm$^{-3}$. The result does not depend on the distance, extinction, or model assumptions. We demonstrate that the found density distribution suggests that the explosion energy of SN~IIP increases with the stellar mass.