In a news release, the Cumberland County Sheriff's Office said the two employees were found unresponsive around 1:30 p.m. and the building was evacuated as hazmat crews were called to the scene.
In a statement released on Monday, Valley Proteins said "this accident may have occurred by lack of following company safety procedures which both employees have been trained in."
Sheriff's Office Major Crimes detectives are investigating. The agency said the names of the workers will not be released following the families' request.
"We are in the process of a full investigation working with all agencies involved to find out what exactly occurred," the statement from the company said.
The company said one of the maintenance workers had worked there for 13 years and the other had been employed for less than one month.
"This is an unfortunate accident and we send our heartfelt condolences to the families of those involved in this tragic event," the company statement said.
Gerald Burke, a mechanic at the plant, said he wasn't sure what happened and didn't hear anything suspicious.
"It's just awful," Burke said. "I don't know what happened."
Valley Proteins recycles oils, animal fats and supermarket waste. It's unclear what the employees were doing at the time of their death or what caused their deaths.
Individuals who know workers at the plant called the news scary and said they were heartbroken for the families of the workers who died.
"Our deepest sympathies are with their families, friends and coworkers during this time," the sheriff's office wrote in a statement.
U.S. Department of Labor documents show this was the third accident at the Fayetteville plant in the last decade. A worker died in 2016 after falling from a ladder and another workers' face was burned in 2013, federal inspection data shows.
Federal documents also show the Valley Proteins' Fayetteville and Rose Hill locations have been fined multiple times over the last few years for various violations spanning from "control of hazardous energy" to machine and equipment issues to respiratory protections.
The North Carolina Department of Labor is currently investigating the deaths to determine if any OSH safety or health standards were violated. The investigation could take up to six months.
Matt Harbin, an attorney with the Law Offices of James Scott Farrin, regularly handles worker safety issues. He said these accidents unfortunately happen regularly.
"I've been practicing this area for over 20 years and these types of injuries haven't decreased. There's still a lot of people that get hurt in accidents that could be avoided," Harbin said.
State data shows 70 workers have died in the workplace since October 2020.
"A lot of industries are, by nature in kind of a dangerous settings where there's toxic chemicals or there's large machinery, big moving parts that creates risk of injury, and those things I don't know how much we can change effectively. I think it's always gonna be a concern," Harbin said.
The Sheriff’s Office responded to Vally Proteins, Inc after two employees were found unresponsive. The 911 call came in just before 1:30pm this afternoon. Hazmat Team is on scene. More details will be released at the appropriate time. pic.twitter.com/XB5rK1rUUo— Sheriff Ennis Wright (@Sheriff_EWright) September 12, 2021
Anyone with information related to Sunday's Valley Proteins incident is asked to call Detective D. Bennett at (910)677-5506 or Crimestoppers at (910)483-8477.