A third man, age 27, was set on fire by the blast and was hospitalized with burns over 80 percent of his body, the Australian Broadcasting Corp. reported.
The explosion occurred about 8:30 a.m. in a wine-processing shed at Drayton's Winery near Pokolbin in New South Wales, the ABC said. Chemicals and a welding incident were believed factors in the blast, the network said.
"We have lost Trevor Drayton," said federal Defense Minister Joel Fitzgibbon. "He's a champion of the wine industry and a leading player in the local vineyard association. He's an expert in his field, a real driving force."
New South Wales Ambulance Service spokesman Terry Watson said there could have been more deaths if the blast had occurred at a different time of day.
"We're not quite sure how many people were in the building at the time but given it was probably before the vineyard opened, the tourists wouldn't have been here," he said.
Drayton's Winery is one of the region's most established vineyards, located in the heart of Hunter Valley wine country, the ABC reported.