A blown transformer forced JCMG to close its main building, 1241 W. Stadium Blvd., Monday afternoon, but officials expected the business to reopen as usual Tuesday.
Lightning may have caused the problem, but Ameren Missouri officials were focused Monday on replacing the transformer, and expected to work on determining a cause later.
Ameren spokeswoman Lisa Manzo said repair crews told JCMG they would be without electricity for the rest of the day, but that weather permitting they would work through the night, if necessary, to replace the transformer and get power restored for Tuesday's appointments.
Janet Wear-Enloe, JCMG's spokeswoman, said the outage began before 11 a.m.
Back-up generators allowed doctors to finish work that already had been started, but the medical group's policies prohibit starting new work or surgeries when only the back-up power is available.
The outage didn't affect phone service, so staff were calling people to cancel their appointments for the rest of Monday.
However, without computer service, "They can't reschedule appointments during the call, and will have to call back later," Wear-Enloe said.
The new Orthopedic Center wasn't affected by the transformer outage, she said.