Residents react to explosion in Logan Township, New Jersey: "Maybe a plane fell out of the sky or something"

At first, David Elze thought lightning or a tree hit the building where he works in Logan Township, New Jersey, as tiles fell from the ceiling Wednesday afternoon.

But it wasn't either of those things — it was something else. 

"That's when we looked around, and we saw the smoke," Elze said. 

"It was pretty startling," he added. 

What Elze and his co-workers heard was an explosion at Savita Naturals in Logan Township, Gloucester County, that critically injured four people. Gloucester County officials said a "large amount of propane" is stored at the facility and is used to process cocoa butter for the chocolate industry.

The explosion was reported at around 2:30 p.m. at the Pureland Industrial Complex at 617 Heron Drive in Swedesboro, according to officials. A shelter-in-place order for a 2-mile radius was in effect for more than an hour, but that has since been lifted. 

Elze works at a building on Heron Drive near the explosion site and said he could see the fire from the explosion over the buildings near his workplace, which he said are about 24 feet tall. It was so powerful that his father, who lives 10 miles away, felt it as well.

"We were concerned about the people who work there, but the first responders showed up immediately," Elze said. "Maybe felt like 60 seconds, the first responder was already there." 

Like Elze, Will Verity was working at a nearby business when the explosion happened. 

"The whole building shook," he said. "The ceiling tiles, crap was falling from the ceiling, the floor shook. It was crazy. We went outside because we didn't know what the hell happened. We thought something hit the roof. Maybe a plane fell out of the sky or something."

Eric Brunhammer works at Thomas Scientific, which distributes medical and scientific supplies, in the 1600 block of High Road, less than a mile from the explosion.

Brunhammer told CBS News Philadelphia that he was working when "something tried to come through the wall."

"It literally sounds like something crashed into the wall of our building," Brunhammer said. "And then our lights flickered, so the next thing I know, people are running outside, so I ran out with them."

Charrell Bird was working at her desk inside her Mullica Hill home, which is about 10 miles away from Logan Township, when she heard a big thud. Her dog then started barking like crazy. 

"I frantically started checking room to room in the house to see, well, did something fall? Did something happen upstairs as far as the roof? Did the roof collapse? I went from room to room and didn't find anything, and that's when I started to get the news alerts that there was a big explosion in the area," Bird said.

Bird said things like this don't happen often, but there are many factories and warehouses in the area. 

"That is a local concern," she said, "that unfortunately, work-related things happen that might impact the community."

The cause of the explosion remains under investigation, according to Gloucester County officials.

Logan Township Police Chief Joseph Flatley said in his 25 years with the department that "this is the largest industrial accident that I can recall."

"At this point, our message to the community is that it was a terrible tragedy that took place out there," Flatley said. "The community is safe. There are no ongoing hazards, and the air quality is continuing to be monitored to confirm that."