Lawmakers on Monday will probe what led to West Virginia's worst coal mining accident in more than 35 years.

Senators from coal mining states are leading the charge to review how 13 miners in the Sago Mine in Tallmansville, W.Va., became trapped for more than 41 hours after an explosion on Jan. 2. Twelve of the miners died of carbon monoxide poisoning. The sole survivor remains in serious condition.

"I don't believe that the federal government is doing enough to protect coal miners from future tragedies," said Sen. Robert Byrd, D-W.Va., the ranking Democrat on the Senate Appropriations Committee, in a statement.

In preparation for Monday's hearing, a delegation of senators planned to visit the Sago Mine site on Friday. Sens. Jay Rockefeller, D-W.Va., Mike Enzi, R-Wyo., Ted Kennedy, D-Mass., and Johnny Isakson, R-Ga., will tour the outside of the mine and talk to victims' families and area miners.

Monday's discussion before the Senate Appropriations Subcommittee on Labor, Health and Human Services, Education and Related Agencies is only the beginning in what will likely be a series of hearings to review miners' safety, oversight of the federal Mine Safety and Health Administration and funding issues. MSHA is the regulatory agency that oversees safety enforcement and health conditions in the nation's mines.

A bipartisan group of 12 senators sent a letter to Senate Health, Education, Labor and Pensions Committee Chairman Enzi and Ranking Democrat Kennedy requesting a series of hearings on budget and staffing levels at MSHA.

"We look forward to sending strong, bipartisan mine safety legislation to the president for his signature before the end of the year. The miners who died at Sago deserve no less," the letter says.

With Congress out of session for most of January, no legislation has been introduced to improve mine safety yet.

Rockefeller, one of the senators asking for additional hearings, noted that the last congressional oversight hearing of MSHA was in 2001.

"We need congressional hearings not only so that we can determine what happened at Sago, but, more broadly, about the state of mine safety across West Virginia and across the country. Coal is on the rise in our country and safety must be too," Rockefeller said in a statement.

Rockefeller said he also has concerns that a reduction in MSHA's budget during five of the last six years has led to fewer inspectors on the job.

A federal investigation of the Sago accident, called for by President Bush, will be led by MSHA and West Virginia officials. Investigators will assess the Sago Mine disaster site once toxic gases disperse.

"MSHA and the state will do all we can to determine what caused this accident so we can continue to improve the safety protections for all miners," said David Dye, acting assistant secretary of labor for mine safety and health.

Dye is scheduled to testify on Monday.

'The World Needs to Be Shocked'

So far this year, 16 miners have died, compared to 57 deaths throughout 2005 and 55 deaths in 2004, according to MSHA statistics. The numbers include deaths in coal, metal and non-metal mines.

Just days after the Sago accident, a coal miner was killed in eastern Kentucky when part of the roof collapsed from a rock fall. On Saturday, the bodies of two miners were located in an underground coal mine in Melville, W. Va. The two miners went missing Thursday night after a fire broke out on a conveyer belt at the Alma No. 1 Mine operated by Massey Energy subsidiary Aracoma Coal. Nineteen other miners escaped.

The last highly publicized mining incident was in July 2002 when nine miners were stuck in a mine in Somerset, Pa., for 77 hours before they were brought up to safety.

The lone survivor of the Sago accident, Randal McCloy Jr., 26, is slowly recovering but remains in a light coma more than three weeks after being rescued. His brother, Matthew McCloy, recently released a picture to The National Enquirer of his injured sibling, saying he wanted to raise awareness of safety risks miners face, saying the government has been kept in the dark about the dangers.

"The world needs to be shocked because we need to have better laws to keep that from happening to other miners' families," Matthew McCloy said in a recorded statement.

The mine's owner, International Coal Group, Inc., has called the mine a "safe operation" despite documents released by MSHA last week that showed 17 of the 208 alleged safety violations in 2005 were listed as serious.

International Coal Group has owned the mine since March 2005. The mine was cited 208 times for alleged safety violations in 2005, compared to 68 citations in 2004. The mine's injury rate for employees per hours worked of 17.4 in 2005 was nearly three times higher than the national average rate of 6.54.

Chief Executive Ben Hatfield, who briefed families and reporters during and after the incident, told reporters that officials "have heard nothing in the course of all this debate about the safety violations that even remotely connects" them to the explosion. Hatfield is expected to testify before the panel on Monday.

A MSHA report dated Dec. 14, 2005, included comments from an MSHA inspector that excessive amounts of loose coal and coal dust in the Sago Mine "showed a high degree of negligence for the health and safety of the miners."

Hearing to Feature Officials, Mine Safety Experts

Monday's hearing will feature representatives for miners, federal mining officials, industry executives and mine safety experts.

The United Mine Workers of America, which represents about 45,000 U.S. miners, wants stronger coal mine safety laws and better enforcement of the oversight agency, said spokesman Phil Smith.

"We need to make sure that MSHA is an agency that enforces the laws," Smith said.

UNWA President Cecil Roberts is expected to testify before the panel.

Bruce Watzman, vice president for safety and health at the National Mining Association, which lobbies for more than 325 companies in the mining industry, is also scheduled to testify.

"I think it's entirely appropriate that they take stock of where we are right now," said Carol Raulston, a NMA spokeswoman. Raulston said NMA will testify on the industry's safety achievements and future plans.

Syd Peng, chairman of the College of Mining Engineering at West Virginia University, told FOXNews.com that Congress should direct money to research safety measures.

Peng said funding is needed to conduct research into the latest safety measures. But as for Sago Mine, Peng acknowledged "we still don't know what caused it" and not much can be done until investigators reach conclusions.

"Coal mining is very much like a subway," Peng said. "You can make it foolproof, but it is so expensive, it is just not economical or practical."