Nearly a year after an explosion erupted at a fuel facility in Tarpon Springs, officials have not determined what caused a gas cylinder to rupture and kill an employee.The state fire marshal's office closed its investigation into the MagneGas Corp. explosion earlier this year, concluding it was an accident, but the agency couldn't identify the cause. Although the Occupational Safety and Health Administration cited MagneGas for several violations, records show they were unrelated to the blast."We were not able to establish the cause," reads an OSHA letter sent to the family of the man killed in the explosion, Michael Sheppard.MagneGas' insurance company hired a fire consultant to determine what went wrong. Company officials said they are still awaiting lab work."We definitely need to find out the cause of the explosion so it can be prevented from ever happening again," said William Corry, a Tallahassee attorney following up on the investigations on behalf of Sheppard's family. "A wonderful young man has lost his life and his mother will mourn the rest of her life."MagneGas is an alternative energy company that creates "clean-burning fuel" with lower gas emissions than fossil fuel, according to its website. The company has about 30 employees that work in a 5,000-square-foot property at 150 Rainville Road, just north of the Sponge Docks district.On April 16 at 1:54 p.m., Sheppard was working with Eric Newell, who had just started working at MagneGas, records state. Together, they were venting a gas cylinder, a routine procedure where the container is flipped to remove any excess fluids. The explosion happened during the process.Sheppard, 29, died at the scene. Newell, now 42, suffered burns and cuts on his back, legs and arms, and was taken to Tampa General Hospital. Newell, who declined comment, still works at MagneGas and was recently promoted to project manager.Records detail the history of the ruptured container. It was purchased new by MagneGas in 2012. In February 2014, it was filled and sent to a company in New York. It was returned eight months later. In March 2015, the 300-cubic-foot tank was tested at a St. Petersburg facility and returned to MagneGas on April 14, two days before it exploded.MagneGas' insurance company hired a fire consultant firm to collect evidence and conduct advanced testing in New Mexico on several cylinders, including the one that ruptured, records show. The state fire marshal investigator noted in his report that he requested information from MagneGas, but was advised there was no official report."This lack of information not shared about the possible causation is concerning for both fire officials and first responders who inspect and respond to these types of events," the fire marshal wrote.But MagneGas CEO Ermanno Santilli said this month that his company never received the request, adding that their investigation isn't over because there is still pending lab work."There are so many factors that they're looking into," he said.But if the fire marshal asked for a report, MagneGas would comply, Santilli said.Following the explosion, OSHA evaluated MagneGas' working conditions. They cited the company on several violations, including lack of employee training on dealing with flammable environments and not requiring flame-retardant clothing.Many of the violations were flagged as serious, defined by OSHA as "when death or serious physical harm is likely to result from a hazard about which the employer knew or should have known."MagneGas paid $52,045 in fines. Records state the violations were not related to the explosion.Since then, MagneGas created a safety director position and hired Bruce Gane."What that did was it made us better," said Santilli of the OSHA evaluation. "Now with Bruce's leadership, we're really following up on everything."Because the company still can't pinpoint what exactly caused the April accident, it completely changed the way it makes its gas, Gane said.Instead of using liquid waste, such as used cooking oil, to produce MagneGas, workers now use soybean oil. The company also switched to more expensive bottles."Everything surrounding that situation has been changed without anybody coming in and telling us to change anything," Gane said.This summer, the company is planning to move to its new 18,000-square-foot headquarters at 11885 44th St. N in Pinellas Park. At the new facility, an explosion-resistant wall made of concrete and rebar separates the equipment from the operators, another extra safety precaution.As MagneGas prepares for its upcoming move, Sheppard's family continues to grapple with his loss.Sheppard, known by his friends as Shep, lived with his mother and stepfather in Safety Harbor. He loved to fish on Honeymoon Island. He was good with his hands, often taking on home improvement projects, like remodeling the kitchen, said his mother, Laurie Fredericks.Sheppard worked for a cabinet shop in Largo, but was laid off in December 2014. In January 2015, MagneGas hired him. Sheppard liked his new job so much, his mother said, that when the cabinetry business said they could hire him back, he declined.On April 16, a fire chaplain and an officer knocked on Fredericks' door."The pain and the hurt, it just doesn't go away. It's been a year, and it's just completely consuming," she said. "He just left that morning for work, and he never came home."Contact Laura C. Morel at [email protected] Follow @lauracmorel.