CHICAGO (CBS) — The lives of four men killed a week ago in a deadly chemical plant explosion were honored Friday morning.

AB Specialty Silicones hosted a memorial at the Waukegan facility with loved ones and law enforcement alike honoring the men. The company says they weren’t only employees; they were family.

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Search crews on the ground spent five days sifting through rubble, looking for the lost.

AB general manager Mac Penman addressed the crowd.

“This has been the hardest week of my life,” he said.

Byron Biehn was a second shift production supervisor for nine years. The 53-year-old was an owner of the company.

Jeff Cummings, 57, was a third shift production supervisor with the company for seven years.

Daniel Nicklas was a quality control chemist. The 24-year-old had been on the job for only eight months.

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Allen Stevens, 29, was also a part-owner of the company and worked on the second shift as a chemical operator.

Nine people were inside at the time of the explosion. Six escaped, including Stevens, who later passed away in the hospital.

AB chemical operator Desmond Woods says he was minutes away from work when the explosion happened.

“I’m still in disbelief just standing here looking at this,” Woods said.

Pastor David Adams says he’s been friends with both Biehn and Cummings for over 40 years. At one time, he called them coworkers.

“We all started here at the same time. Now, we got grandchildren together,” Adams said. “They were wonderful guys — simple, hardworkers, faithful.”

Fire investigators say they believe last Friday’s blast was a result of an accident in factory processes. The investigation process could take months and involves both state and federal agencies.

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The business is expected to reopen next Monday.