WICHITA, Kan. (KSNW) – At least 15 people were injured Friday when a nitrogen line exploded at the Beechcraft aircraft manufacturing facility causing part of the building to collapse, authorities say.

Daniel Wegner, deputy fire chief for Sedgwick County, said the explosion happened at around 8 a.m. at the facility. John Gallagher, the county’s EMS director, said 11 people were taken to hospitals and four were treated at the scene. No one was killed.

“I can not describe how bad that was and what was going through my head,” one employee remembers. “I know I needed to get in there to help people, but I couldn’t because I did not know if there was going to be more explosions or what.”

Workers inside the plant at the time say some were disoriented after hearing what they call an explosion.

“What felt like an earthquake,” said one person who was in the building at the time. “It was like an explosion there is no other way to describe it. I saw darkness and dirt in the air. I saw everything moving around because, like I said, there was a pretty big explosion. And the walls were flexing and the wall I was standing next to, it moved four feet.”

Wesley Medical Center said they received five patients. Four of which have been treated and released. Only one patient remains in the hospital in fair condition, said a spokesperson at Wesley Medical Center.

Ascension Via Christi St. Francis‎ said they received seven patients by ambulance and two by private vehicle. All seven have been released from the hospital.

Wegner said the explosion happened when a 3-inch liquid nitrogen line ruptured.

“The lines that were ruptured as I told you earlier were shut down, we’re currently off-gassing a couple of tanks to one-inch valves, which is going to take about 30-45 minutes to off-gas the rest of the nitrogen,” Wegner said.

The gas posed no risk to nearby residents, officials said.

“The plant closed or shut down for the holiday season so the numbers that would have been here, were not, so it was a skeleton crew,” Wegner said.

Wegner said crews are doing building assessments and looking at the structural integrity of the surrounding structures that could have been impacted.

“It’s got extensive damage in there and that’s why the engineers and stuff are going to go in there and do a better assessment of the amount of damage in the building,” Wegner added.

Stephanie Harder, a spokeswoman for Beechcraft’s parent company, Textron Aviation, said the structure where the explosion happened is part of a complex of buildings and houses the business’ composite manufacturing and experimental aircraft or Plant 3.

The cause of the blast is under investigation.

“Our simple role is to assist with any investigation that needs to take place. OSHA is on-site, Textron has their folks here as well. So when the building becomes structurally sound, we will assist in any way possible that OSHA needs to document what has occurred here,” said Sedgwick County Sheriff Jeff Easter.