The blast occurred about 3:30 p.m. at the Airgas Mid America facility in the unincorporated community of Black Betsy in Putnam County, The Charleston Gazette reported.
The victims were taken to Cabell Huntington Hospital with first- and second-degree burns, officials at the accident scene said. One had burns to his face and the other to his arms, an official told the newspaper.
Emergency officials said it appeared about 50 cylinders of acetylene were the source of the explosion, which produced a fire witnesses said sent flames shooting from the plant.
Bancroft Volunteer Fire Department said firefighters had the fire "out for the most part" by about 4 p.m.
Jones said about 100 cylinders were stored in the area where the explosion occurred, and about 50 of them exploded.
An employee said five of the plant's 10 employees were at the site when the explosion happened, the Gazette said.
The newspaper said U.S. Environmental Protection Agency data compiled by a public interest group that monitors chemical safety show the Airgas facility reported having on hand up to 76,000 pounds of propylene and up to 10,000 pounds of propane. However, there was no EPA information included about acetylene at the plant, the Gazette said.
The blast, which could be felt about a half-mile away, led authorities to close nearby Highway 62.
Doug Barker, chief financial officer of Clark Truck Parts, located a half-mile away, said there was an initial explosion that was "really big," followed by a series of smaller ones. He said he first saw a huge cloud of black smoke and flames.