The KARMEN experiment at the Rutherford Appleton Laboratories has recently reported a timing anomaly in their neutrino arrival time distribution from stopped muon decays, which may be evidence for an exotic neutral particle with mass of 33.9 MeV. The E815 (NuTeV) neutrino experiment has recently performed a search for this 33.9 MeV weakly interacting neutral particle produced in pion decay using a dedicated decay channel. This talk will present the results of this and other searches for massive weakly interacting neutral particles.