Associated primes of local cohomology modules

Let $\mathfrak{a}$ be an ideal of a commutative Noetherian ring $R$ and $M$ a finitely generated $R$-module. Let $t$ be a natural integer. It is shown that there is a finite subset $X$ of $\operatorname{Spec}R$, such that $\operatorname{Ass}_R(H_{\mathfrak{a}}^t(M))$ is contained in $X$ union with the union of the sets $\operatorname{Ass}_R(\operatorname{Ext} _R^j(R/\mathfrak{a},H_{\mathfrak{a}}^i(M)))$, where $0\leq i<t$ and $0\leq j\leq t^2+1$. As an immediate consequence, we deduce that the first non- $\mathfrak{a}$-cofinite local cohomology module of $M$ with respect to $\mathfrak{a}$ has only finitely many associated prime ideals.