New details have emerged about the cause of the Alabama gas pipeline explosion that left one worker dead and four hospitalized Monday.

The blast on the Shelby County stretch of the Colonial Pipeline was the result of a worker accidentally hitting the line while doing excavation work for the company, Gov. Robert Bentley said Tuesday.

"On October 31, 2016 at 2:55 p.m. a Colonial Pipeline contractor struck a 36" below ground transmission gasoline pipeline while unearthing threaded O-rings (TOR) for rendering the line inert," Bentley said in a press release. "This operation was necessary to install a permanent repair required by the previous pipeline rupture on September 9, 2016."

Colonial spokesman David York told AL.com earlier Tuesday afternoon that the company was not yet sure what exactly had precipitated the explosion, though he said an investigation into its cause was underway.

"We were excavating the pipe to do some work to help facilitate the installation of new pipe to where the leak actually took place," York said when asked what the workers were doing when the explosion occurred Monday.

At the time, he said that the exact cause of the blast was not yet known.

"What happens with these things - especially when you have a release of gasoline because it's more volatile - it's the right mix of the fuel, the oxygen level and then the ignition source," he said. "You had all three come together in this event here."

He emphasized that the company had yet to determine the ignition source that allowed the gas to catch fire.

"There was an ignition source. We don't know what that was and we will not know that until we conclude our investigation," he said. "It could have been a spark from a piece of excavation equipment or from a pickup truck nearby. We will be looking that in our investigation in the coming days."

At this early stage of that investigation, it is not yet known whether any issues with maintenance or age of the pipeline played a role in the explosion or made it more likely to occur.

A Colonial spokesperson told AL.com last month that the last time a machine called a "smart pig" was sent through the Shelby County stretch of the company's pipeline was in 2014.

"Colonial ran a tool through the area in 2009 and again in 2014," the spokesperson said. "If they see something during the smart pig run, they go out and do some maintenance sometimes."

Asked about the potential for the condition of the line to have been a factor in the pipeline's susceptibility to breaking, York said, "[w]e just don't know at this point. We don't think so but we cannot say so right now."

Updated on Nov. 1 at 8:15 p.m. to fix the wording about the smart pig.