CHARLESTON, W.Va. -- Federal investigators arrived Monday at the West Virginia mine where 29 men died in an explosion last week to begin piecing together what caused the worst U.S. coal mining disaster since 1970.

Thirty miles to the north, hundreds of mourners, including the governor, observed a moment of silence at the state Capitol during a wreath-laying ceremony at the foot of a statue honoring the state's miners. Karen Barker was among scores of state workers who attended the ceremony.

"My dad was a miner and my grandfather was a miner. I have no idea how these people feel about losing their family member, but I can imagine," said Barker, 46, of Charleston, W.Va.

The team of inspectors at the Upper Big Branch mine weren't heading underground until searchers finished the grim task of removing the final nine bodies from the mine. The team from the Mine Safety and Health Administration briefed Secretary of Labor Hilda Solis and MSHA director Joe Main at the mine.

The last bodies were expected to be taken out of the mine Monday afternoon, state mine office spokeswoman Jama Jarrett said. Recovery efforts had been stalled in previous days by volatile gases, but teams had entered by early Monday after the tunnels were ventilated.

Jarrett said the crews late Monday were near where the bodies are located.

The state panel that writes mining safety rules and typically reviews mine inspectors' reports after the investigations are complete said Monday that it would like to join the investigators underground this time.

Richmond, Va.-based Massey Energy Co., which owns Upper Big Branch mine, has been under scrutiny for a string of safety violations at the mine.

Authorities have said high methane levels might have played a role in the disaster. Massey has been cited and fined repeatedly for problems with the system that vents methane and for allowing combustible dust to build up.

Mourning continued Monday, exactly a week after the explosion, with the ceremony at the state Capitol and a moment of silence at 3:30 p.m. President Barack Obama on Monday ordered all U.S. flags in the state flown at half-staff until sunset Sunday.