Please answer the following question about this movie plot. If it's un-answerable, please output "No answer". Question: What was discovered in a cave near Del Rio, Texas? Movie plot title: Nightwing Movie plot: Deputy Youngman Duran [Nick Mancuso] and Walter Chee [Stephen Macht] are both looking out for the survival of the Southwestern American Indian. So is Doctor Anne Dillon [Kathryn Harrold], who is forced to birth babies without even the barest of technology. So is tribal priest Abner Tsupi [George Clutesi], who foresees the death of his people and has decided to 'end the world' so that his people stand a chance of survival.When a horse is found dead of multiple punctures and smelling of ammonia, Duran and Chee argue over who should handle the investigation. Duran wants to keep it tribal while Chee wants to call in federal investigators and people from the Peabody mining company who have found shale in the burial ground. When Anne and a group of tourists are attacked by vampire bats, Duran and Payne [David Warner] set out to find her. Together, they track the bats to a cave in the burial ground and set it on fire. The fire will burn forever, and there will be no mining. This was how Abner intended to 'end the world' and to save his people. Everything else--the bats, Duran, religious legend, etc.--were all pawns in Abner's plan.The movie ends with the warning--"In recent years, vampire bats were discovered and destroyed in a cave in Val Verde County near Del Rio, Texas."
A:
Vampire bats