(NBC) - The House Education and Labor Committee meets Monday in West Virginia, about an hour from the Upper Big Branch Mine where 29 workers died last month.
The issue is whether a string of violations there led to that disaster.
"We know it wasn't operating safely, or we wouldn't have had an explosion," Mine Safety and Health Administration Kevin Stricklin said.
President Barack Obama, who spoke at the miners' memorial, blamed Washington. There's a backlog of 16,000 safety cases on appeal.
"A failure of laws so riddled with loopholes that they allow unsafe conditions to continue," said Obama.
He's asked the Labor Department to tighten its rules, to make it easier to prove a pattern of violations.
The mine owner told Congress last week safety is his No. 1 priority.
"We've led the industry in safety innovation, and we've made every attempt to deal with the violations," CEO of Massey Energy Company Don Blankenship said.
But West Virginia's Senator Robert Byrd disagrees: "Blatant disregard for the safety of Massey miners. Shame!" he said.
West Virginia's Governor and victims' relatives will testify Monday.