# Weierstrass points on modular curves

What is knowns about Weierstrass points on modular curves? Are there any explicit formulas of them, or any information about Weierstrass gaps? I am interested in (compactifications of) the quotients of the upper half plane by $\Gamma(n)$, $\Gamma_1(n)$ or $\Gamma_0(n)$. The level $n$ may be assumed to be prime, if that helps.