Two UPS employees were killed Monday, Nov. 25, in a workplace accident at the package-delivery service’s hub at Ontario International Airport, Ontario police said.

UPS spokesman Steve Gaut said the accident happened sometime before 6 a.m. and involved two part-time package handlers.

Luke Brown, a spokesman for Cal/OSHA, which investigates workplace accidents, said the victims were on what is called a tug. UPS Airlines said in a Twitter message that tugs pull dollies that are loaded with containers to be loaded onto airplanes. Some tugs have tops. The one the victims were in did not.

“I want to express my condolences to the friends and family and co-workers and everyone who knew the employees,” Gaut said.

The victims’ identities have not been publicly released.

Packages are sorted for distribution via ground and air at the facility, which underwent an expansion to double its sorting capacity in 2016.

Pep Rally time for Ontario Morning Sort!!! The Mighty M-sort, you guys are THE best! Here is our Division Manager, Brian Lorton, speaking to everyone about SAFETY this Peak Seson! This is before our mascot did his dance moves! @jrindafernshaw @gaze_anthony @melirere @brose_ups pic.twitter.com/7WY5tbDZ1j — Kellie Rathbone (@RathboneKellie) November 25, 2019

On Sunday, a UPS employee posted a video to Twitter that shows a supervisor at the Ontario facility talking to sorters about safety.

“Take care of yourselves. Please, please, please,” he says, speaking through a bullhorn.

Gaut said he had not seen the video but noted that similar meetings take place before every shift where supervisors encourage the employees and provide a safety message.

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“We are focused on people using safe work habits while we deal with the additional holiday volume,” Gaut said.

There have been occasional ,serious accidents at the site, according to the Cal/OSHA website.

On Nov. 13, 2018, an employee was coupling dollies. When he “over gripped” the handle of the second dolly, he struck his right middle finger against the rear coupling area of the front dolly, the website says. The middle finger of his right hand was amputated.

At 6:15 a.m. on May 25, 2018, an employee was climbing a ladder to a cargo carrier and reached for the gate on the top platform with his left hand. The employee missed and fell approximately 10 feet to the ground, the website says, fracturing a rib and leg and breaking his nose.