According to Travel Pulse:

A power outage around 4 p.m. Friday cut opening day short at Six Flags St. Louis, the St. Louis Post-Dispatch reported.

Six Flags St. Louis tweeted “We have experienced a power outage in the park. All guests are currently being escorted off of the rides.”

On Saturday, the Six Flags St. Louis Twitter page had an update: “Yesterday we experienced a power outage due to an underground fault. Ameren UE has repaired the line and the park will open as scheduled.”