Magnetic reconnection plays an important role in determining the evolution of magnetic topology in laboratory and astrophysical plasmas. A central question concerns why the observed reconnection rates are much faster than predictions made by classical theories, such as the Sweet-Parker model based on MHD with classical Spitzer resistivity. Often, the local resistivity is conjectured to be enhanced by micro-instabilities to accelerate reconnection rates either in the context of the Sweet-Parker model or by facilitating setup of the Pestchek model. Although it is commonly believed that there is plenty of free energy available at the reconnection region to destabilize some sort of micro-instability, a clear identification of this instability and its exact role in reconnection has never been established experimentally. We report the first such experimental evidence of a clear and positive correlation between magnetic fluctuations in the lower-hybrid frequency range and resistivity enhancement during fast reconnection in the low-collisionality regimes in the Magnetic Reconnection Experiment (MRX). The waves have been identified as right-hand polarized whistler waves, propagating obliquely to the reconnecting field, with a phase velocity comparable to the relative drift velocity. These waves are consistent with the modified two-stream instability driven by large drift speeds compared to the Alfven speed in high-beta plasmas. The short coherence length and large variation along the propagation direction indicate their strongly nonlinear nature.