One of the deceased, 47-year-old Scott Thrower, had suffered burns on Thursday after the explosion at the Williams Olefins plant in the industrial area of Geismar.
He died on Friday at the Baton Rouge General Medical Centre, Louisiana police said.
The explosion also claimed the life of 29-year-old Zachary Green who succumbed to his injuries on Friday.
Indian-American Louisiana Governor Bobby Jindal condoled the death of workers.
"Our thoughts and prayers are with the workers and families at the Olefins plant," Jindal said. "We are going to provide every assistance we can to help them get back on their feet."
The plant was in the process of expanding and the explosion occurred in a propylene fractionation area, which makes propane and propylene, a highly-flammable chemical, the plant manager, Larry Bayer, said.
The investigation into the cause of the blast is ongoing.
"The company is working with regulators to investigate the cause of the explosion, assess damages at the 25-acre site and reopen the plant, which Williams Cos has owned since 1999," CEO Alan Armstrong said.
At present, two Williams employees and four contractors remained hospitalised, Armstrong said, adding that about 100 others were being treated for injuries.
About two dozen workers are at the plant in 12-hour shifts to ensure its safety as residual hydrocarbons are burned off through a smokestack, Bayer said.
The company is working with the Occupational Safety and Health Administration to assess the plant's structural integrity.
"We are devoted to operating a safe facility. We are very proud of our safety record," Bayer said.
"Once we better understand the cause we certainly will be taking necessary steps to prevent this from ever happening," Armstrong added.
He also said that employees would be paid while the plant is temporarily closed, but that it was not clear how extensive the damages are or how long it will take to reopen.
The US Environmental Protection Agency has also dispatched staff to the plant to monitor potential environmental effects.
The explosion comes two months after 15 people died following a fire and twin blasts at a fertiliser plant facility in Texas.