Imagine waking up to a 22-foot-deep hole outside your house where your sidewalk used to be. This is exactly what several folks in a Williamson County neighborhood woke up to Thursday morning. What residents thought was a thunderstorm in the early morning turned out to be a massive sink hole forming.

Williamson County officials tell KXAN that it’s still not clear what caused the collapse or whether the utility lines played a role, but they did note that outside the area where the utility lines are located, the cave ceiling is stable.

“It looks like the roof of the cave just collapsed and when it collapsed it broke our water line and also exposed a natural gas line,” said Mike Petter, general manager for Brushy Creek MUD. He expects the road there will be closed for a few weeks.

While the utility district encounters caves often, this is the first time they’ve seen a neighborhood cave of this size and a spontaneous collapse like this, Petter said. KXAN asked Petter if homeowners should be worried about the safety of their homes.

“There are probably a lot of homes in Brushy Creek that are built over cave features and we’ve seen that and it will really take an engineer to look at the stability,” he responded, adding that engineers would be headed in to evaluate the cave on Friday. Brushy Creek MUD says their initial review shows the cave is 22 feet deep, 40-50 feet wide and 170 feet long.