  Let $R$ be a commutative Noetherian ring of prime characteristic $p$. In this
paper we give a short proof using filter regular sequences that the set of
associated prime ideals of $H^t_I(R)$ is finite for any ideal $I$ and for any
$t \ge 0$ when $R$ has finite $F$-representation type or finite singular locus.
This extends a previous result by Takagi-Takahashi and gives affirmative
answers for a problem of Huneke in many new classes of rings in positive
characteristic. We also give a criterion about the singularities of $R$ (in any
characteristic) to guarantee that the set of associated primes of $H^2_I(R)$ is
always finite.
