We analyze nonnegative solutions of the nonlinear elliptic problem ∆u = λf (x) u 2 + P , where λ > 0 and P ≥ 0, on a bounded domain Ω of R N (N ≥ 1) with a Dirichlet boundary condition. This equation models an electrostatic-elastic membrane system with an external pressure P ≥ 0, where λ > 0 denotes the applied voltage. First, we completely address the existence and nonexistence of positive solutions. The classification of all possible singularities at |x| = 0 for nonnegative solutions u(x) satisfying u(0) = 0 is then analyzed for the special case where Ω = B1(0) ⊂ R 2 and f (x) = |x| α with α ≥ 0. In particular, we show that for some α, u(x) admits only the "isotropic" singularity at |x| = 0, and otherwise u(x) may admit the "anisotropic" singularity at |x| = 0. When u(x) admits the "isotropic" singularity at |x| = 0, the refined singularity of u(x) at |x| = 0 is further investigated, depending on whether P > 0, by applying Fourier analysis.