When did build the heavy duty cages around the caves at Stone Oak Park?

This is something I’ve been curious about, when I was living in San Antonio in the mid 2000’s, one of my favorite things to do was to explore the caves at Stone Oak Park. Cub Cave was totally unobstructed, and while Bear Cave had a metal grate atop the sinkhole, it was easy to slide underneath and there was a rope secured to it to help get down and back up. I got pretty deep into Bear Cave, it was really amazing in retrospect to be able to roam freely throughout the cave. Now, there are sturdy velociraptor cages with angled slats and absolutely no way in without serious heavy equipment. When were these cages installed, and was there an incident that led to them, or was it to preserve the ecosystem? I certainly recognize that it’s probably for the best that these caves are closed to the public, they are delicate ecosystem, and spelunking is best left to the people who actually know what they’re doing.