The information loss paradox associated with black hole evaporation is an unresolved problem in modern theoretical physics. We consider the evolution of the black hole entanglement entropy via the Euclidean path integral of the quantum state under the semi-classical approximation. We argue that there exist Euclidean instantons that mediate the tunneling from a black hole geometry to a trivial geometry where all the black hole mass is carried away as radiation. By taking into account the multiple classical histories resulting from the tunneling, we recover the Page curve for the entanglement entropy, albeit being modified, with its maximum largely exceeding the Bekenstein-Hawking bound.