Updated 9:46 p.m. ET
The Massey Energy coal mine where 25 people died in an explosion was cited for violating for two federal safety violations on the day of the blast.
Mine Safety and Health Administration records show the citations were issued Monday. The records do not specifically say whether they were issued before the explosion.
Massey spokesman Jeff Gillenwater says neither violation was life-threatening. Kevin Stricklin, a top federal mine official, says he is confident the violations had nothing to do with the blast.
Records show one of the violations involved inadequate maps of escape routes from the Upper Big Branch mine. Underground coal mines are required to have maps detailing escape routes, oxygen caches, and refuge chambers.
The other involved an improper splice of electrical cable on a piece of equipment.
as rescuers worked to vent dangerous gasses from the mine to make it safe to reenter.
Crews had drilled one hole and were working on several more to release enough methane gas so searchers could enter the Upper Big Branch mine to look for four people still missing in the worst U.S. mining accident in more than two decades.
At a 3:30 p.m. press conference, West Virginia Gov. Joe Manchin and federal mine safety officials said that the methane, carbon monoxide, and hydrogen levels in the mine still far exceeded the level at which rescuers could safely reenter - even with oxygen masks.
The gases are so strong that they were even affecting the drill operators working near the holes above ground. The mine owner installed an angled pipe to redirect the exhaust.
The disaster has brought new scrutiny for mine owner Massey Energy Co., which has been repeatedly cited for problems with the system that ventilates highly combustible methane gas. The federal Mine Safety and Health Administration on Wednesday appointed a special team of investigators to, which officials said may have been caused by a build up of methane.
In 2009, Upper Big Branch was cited 50 times for "unwarrantable failures." And 38 times inspectors wrote "ventilation violations" - a repeated sign the mine was failing to properly remove explosive gases, reports CBS News correspondent Bob Orr. Investigators suspect it was a buildup of methane gas that triggered Monday's blast.
Former mine safety official Celeste Monforton says it's clear that critical warnings were ignored.
"This is not an accident. This is not an accident," Monforton told Orr. Mining engineers dating back 100 years have understood the fatal mix of coal dust and methane and we know how to control those."
But, the mine was not shut down. And Massey repeatedly frustrated regulators. Last year Massey paid only a fraction of the $900,000 in fines levied against Upper Big Branch mine.
That's because Massey appealed 35 percent of the 515 alleged violations, including the most serious ones. By contrast, in 2005 - the year before mine safety laws were toughened - Massey's appeal rate was only four percent.
Like many other mine operators, Massey frequently sidesteps hefty fines by aggressively appealing safety violations at the mine, according to an Associated Press analysis of mine safety records.
Former safety officials say Massey and other coal operators are now using a legal strategy to fight back against tougher standards.
More on the mine disaster:
Miners Families Cling to "Sliver of Hope"
Mine CEO Doesn't Rule out Violations as Cause
W. Va. Coal Mine Blast: The Victims
List Of Recent Fatal U.S. Mine Disasters
In Coal Mines, Risk of Death Is Part of Life
Mines not Paying Fines a Familiar Story
Gov.: "No Excuse" for Mine Safety Flaws
Eerie Statement from Miner Killed in Blast
Mining Company Previously Fined for Safety
The quality and quantity of coal produced at Upper Big Branch make the mine one of gems of Massey's operation. The mine produced more than 1.2 million tons of coal last year and uses the lowest-cost underground mining method, making it more profitable. The mine produces metallurgical coal that is used to make steel and sells for up to $200 a ton - more than double the price for the type of coal used by power plants.
Federal regulators probing the explosion plan to review Massey's safety violations, many of which involved venting methane gas. If the odorless, colorless gas is not kept at safe levels, a small spark can ignite it.
"They had a doubling of their citations from 2008 to 2009. They had a tripling of the penalties," former mine safety official Davitt McAteer told Orr. "That period suggests to you that you've got a problem."
Massey CEO Don Blankenship drew criticism four and a half years ago with an internal memo to supervisors in which he seemed to stress productivity over safety, saying, "We seem not to understand that coal pays the bills."
"Even if it wasn't stated, if you're saying that production is the most important part of our operation, you're implying that safety is not the most important part," mine safety attorney Tony Oppegard told Orr.
But Blankenship later said his memo had been misconstrued and that safety was not "secondary."
"We've cut the accident rate at Massey probably about 90 percent over the time that I've been president … Our goal is zero," Blankenship told Smith in
Blankenship has said that Massey's safety is better than the industry average. But, federal safety records reveal that Upper Big Branch mine has a history of violations suggesting it's been more dangerous than most.
Over the past two years, Upper Big Branch has a violation per inspection day rate that's higher than the national average. And in terms of "serious" violations it's higher still.
Only 1.5 percent of all violations industrywide were considered serious. At Upper Big Branch, the percentage was five times that - nearly 8 percent, Orr reports.
Joseph Main of the Mine Safety and Health Administration said they will begin an investigation into Massey once the rescue effort is completed.
"It's very obvious that something seriously went wrong at this mine," Main told CBS' "The Early Show" Wednesday. Saying a probe would take weeks and months to complete, Main vowed a "pretty extensive investigation."
Appearing Tuesday on CBS' "The Early Show", Gov. Manchin said there would beif safety violations were found to have contributed to the accident.
Massey is still contesting more than a third of all its violations at the Montcoal, W.Va., mine since 2007. In the past year, federal inspectors have proposed more than $1 million in fines for violations at the mine. Only 16 percent have been paid.