Workplace safety investigators have launched a probe after a longtime U.S. postal carrier was found dead in her mail truck in Woodland Hills amid record-breaking heat Friday.

“We can confirm that federal OSHA (Occupational Safety and Health Administration) has started an investigation,” a spokesman for the U.S. Department of Labor said in an email Tuesday. “Please note that because this is an open case we cannot provide any further information at this time.”

Peggy Frank, 63, of North Hills was found unresponsive while seated in a postal vehicle in the 4800 block of Calderon Road by a co-worker or bystander, said Ed Winter of the Los Angeles County Department of Medical Examiner-Coroner’s office.

Emergency personnel attempted to revive her but she was pronounced dead at the scene at 3:35 p.m. Friday.

RELATED STORY: U.S. Postal Service worker found dead in Woodland Hills amid Friday’s record-breaking heat

Temperatures soared to 117 degrees in Woodland Hills on Friday, surpassing the record of 106 degrees for that day, July 6, that was set in 1976. (The National Weather Service has kept records there since 1949, according to Keily Delerme, a NWS meteorologist.)

But it is not yet known whether the extreme heat was a factor in Frank’s death. While her autopsy had been completed, the cause of death was deferred pending additional tests, Winter said. Those tests are expected to take between four and six weeks.

The veteran mail carrier also had a medical history but Winter declined to elaborate until the final cause of death is determined.

Colleagues said Frank, who had worked for the U.S. Postal Service for 28 years, had recently returned from medical leave when she died.

OSHA became aware of Frank’s death after the agency was contacted by emergency service personnel, the Department of Labor spokesman said.

OSHA would open an investigation in many situations involving a work-related fatality and when the nature of the fatality is unclear, according to the agency’s website. If a fatality is clearly due to natural causes, the OSHA area office director can forego an investigation.

Employers are obligated to protect employees from any hazardous condition, including potential heat stress, according to the Department of Labor.

“Every year, thousands of workers become sick from occupational heat exposure, and some are fatally injured,” OSHA states on its website. “These illnesses and fatalities are preventable.”

A U.S. Postal Service spokeswoman said earlier this week that carriers deliver mail in “all kinds of weather, including high temperatures.”

“The Postal Service strives to ensure that they have the tools and training to do so safely,” spokeswoman Evelina Ramirez said.

Carriers are reminded daily to stay hydrated throughout their route, wear appropriate clothing, such as hats, and get into the shade whenever and as much as possible, Ramirez said.

Deborah Miller, a retired U.S. Postal Service worker who used to work with Frank, suggested that in extreme weather, the Post Office should call a no-delivery day.

When Miller worked at the Santa Clarita Post Office for over a decade, she said the postmaster once told her she could work inside or go home due to high levels of particulates in the air from a fire. She went home that day, she said, and had to use a no-pay or vacation day.

“If it was the heat (that contributed to Frank’s death), it shouldn’t have happened,” Miller said.

While working in severely hot weather in the San Fernando Valley, Miller said she would just “suck it up.”

“You find a hose or sprinklers, anything that you can go to get refreshed,” she said.

Postal carriers at the Woodland Hills Post Office told this news group that their mail trucks do not have air conditioning and can get extremely hot inside.

As of the fall of 2017, U.S. Postal Service’s fleet of service vehicles included more than 230,000 purchased and leased vehicles, including about 162,000 older right-hand drive delivery vehicles, according to a spokeswoman with the agency. Of those older right-hand drive vehicles, about 141,000 “have exceeded their expected life.”

The Postal Service has been conducting research and testing as part of an effort to operate a future class of delivery vehicles that will incorporate “new technology to accommodate a diverse mail mix, enhance safety, improve service, reduce emissions, and produce operational savings,” said Kim Frum, a spokeswoman with the U.S. Postal Service Headquarters, in an email.

She did not say whether that technology will include air-conditioning, anti-lock brakes or air bags, which at least some postal vehicles reportedly do not have.

The agency is also evaluating a number of commercial vehicles for potential use as well.

“Our goal is to obtain vehicles that will help us provide reliable and efficient delivery service for customers while meeting the needs of our employees to best do their jobs safely,” Frum said.

In July 2012, a mail carrier in Independence, Mo., collapsed while working his route and died as a result of his exposure to excessive heat. An OSHA investigation found that the Postal Service “did not have procedures in place to address worker concerns during times of excessive heat,” according to the administrative agency.

The Postal Service was required to pay a penalty of $70,000 in that case, according to the news site Fox4KC.com.

In October of 2016, OSHA cited the Postal Service after two Des Moines, Iowa, workers suffered heat-related illness while delivering mail that past summer. The agency found that the two mail carriers, one of whom was told to continue walking her route despite feeling ill, were exposed to excessive heat.

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