SANTA CLARA — In a rare turn, the state’s workplace safety watchdog rescinded a notice of no violation and reopened its investigation into the death of a veteran elevator mechanic who died in June while working on the new 49ers stadium.

Cal-OSHA originally sent the notice to Schindler Elevator on Oct. 14 following its investigation into the death of Donald White, who was standing on a ladder at the bottom of one of the stadium’s elevator shafts when he was struck by a counterweight and killed.

But during a subsequent internal review of the case, “one of the experienced Cal-OSHA people raised questions,” and the decision to reopen the accident investigation was made, according to spokeswoman Erika Monterroza.

“This does not happen on a regular basis,” Monterroza said.

Monterroza did not state what questions were raised in the internal audit. She said investigators are “carefully going over all of the evidence’ to make sure the investigation is complete.”

Cal-OSHA has until Dec. 11 to finalize its investigation.

“We are aware, and were surprised to learn that Cal-OSHA has rescinded a notice of no violation, Schindler Elevator said in a statement. “We believe there was no safety violation on the job site and that Cal-OHSA’s notice of no violation remains an appropriate conclusion. Nevertheless, we will continue to cooperate with the investigation.”

The company also said: “Our thoughts remain with Mr. White’s family.”

In 2011, Schindler was fined $18,000 after an apprentice elevator mechanic fell about 19 feet down a shaft while doing work related to the installation of a new hydraulic elevator in Palo Alto. Cal-OSHA determined it could have been avoided had the apprentice been wearing fall-protection equipment, according to a report. The worker survived the fall but suffered several broken bones, including a vertebra and pelvis.

Cal-OSHA is also in the midst of investigating a second workplace death at the 49ers new $1.3 billion stadium project.

On Oct. 15 a worker was killed while unloading a bundle of rebar — steel bars commonly used to reinforce concrete — from a flatbed truck when it fell on top of him, causing serious injuries. The worker, Edward Erving Lake II, a 60-year-old Vacaville resident, was taken to the hospital, where he was pronounced dead.

Contact Mark Gomez at 408-920-5869. Follow him on Twitter @MarkMgomez.