Employees of Liberty Casting Co. remain shaken by an explosion and fire that injured five workers in a foundry Aug. 21 as investigators continue to look into the cause.

Delaware Fire Chief John Donahue said his department is considering a range of possible causes, from human error to equipment malfunction.

"The true picture is not visible until you have the final pieces," he said. "Right now, we just have the corners."

The first rescue teams arrived to 550 S. Liberty Road about five minutes after the 911 calls came in about 10:10 p.m.

"I've got multiple injuries ... multiple guys who are burned up," a worker named Eddie told a 911 operator. "I need multiple EMS here."

During the five-minute call, shouts and moans could be heard in the background among the 14 or 15 workers who were beginning third shift at the time.

The caller described one of the more serious injuries: "His skin's melted off his entire back."

Donahue said fire crews arrived to find a complicated scene.

"It was an explosion, and then you have spot fire throughout a large manufacturing area," he said.

Much of the damage apparently was caused by molten metal thrown from a furnace, Donahue said. The secondary fires, mostly extinguished by employees, were contained within about 20 minutes.

Four patients were taken by ambulance and helicopter to the burn center at Ohio State University's Wexner Medical Center. Their names and conditions have not been released, though one of them had been released from the hospital by Aug. 29. A fifth patient was treated at OhioHealth Grady Memorial Hospital in Delaware and released.

Two of the more seriously injured had burns around their faces and mouths, Donahue said.

"The problem with burns is that you have the initial damage and then later, the swelling and complications," he said.

According to the company's website, Liberty specializes in "gray, ductile and high alloy iron casting."

The fire department has responded to other emergencies at the plant, Donahue said, including a forklift fire in June 2014, a flammable liquid leak and fire in 2012 and a furnace fire about 10 years ago.

There was little evidence Aug. 22 of the chaos the night before. Employees came and went from a full parking lot, declining to answer questions.

An employee in human resources said the company would have no comment. "We are handling this ourselves," said the employee, who declined to be named.

Occupational Safety and Health Administration spokesman Scott Allen confirmed the incident will be investigated. He said witnesses already have been interviewed to determine a cause and if OSHA safety standards are being followed. By law, the agency must complete its investigation within six months.

OSHA inspectors have cited Liberty Casting for 26 violations since 2010, resulting in about $76,000 in fines, according to the agency's records. Of those violations, 20 were considered "serious." The two most-recent violations came following a 2015 inspection, when the foundry was cited for two serious violations concerning the control of hazardous energy.

Employees were using propane torches without wearing flame-resistant clothing, and employees were unclogging valves without proper training, according to the citations.

Donahue said he likely will have more details and a possible cause soon, after the injured can be questioned.

"I'd hate to say it's one thing when it's something else," he said.