U.S. Mine Safety and Health Administration officials just ended a media briefing, held via telephone call, in which they provided a bit of an update on the status of their investigation into the Upper Big Branch Mine Disaster.

Here’s a quick rundown of the high points:

— While it wasn’t part of the MSHA chief Joe Main’s opening statement, Main and his coal administrator, Kevin Stricklin, did confirm what they told Upper Big Branch families in a closed door-meeting last evening: MSHA flatly contradicts Massey Energy’s previous statements that investigators have found a “massive crack” in the floor of the longwall section of the mine.

Massey has pointed to the crack as a potential sign of a huge methane outburst, as part of the company’s “act of God” theory about what caused the explosion.

But Main and Stricklin said their investigators have not found any crack of the sort Massey has described to the media and to the Upper Big Branch families:

I have seen nothing to represent a crack that large, nor have I talked to anybody who has.

Stricklin said investigators have found smaller cracks and signs of floor heaving, but nothing of the sort that Massey has described.

— MSHA officials described their investigation as massive — with 166 interviews (up from 126 reported by Davitt McAteer on July 14), several hundred pieces of evidence and 1,800 rock dust samples collected to date. Still, investigators have only examined about half of the mine, and have not made it into two key areas, the continuous mining “development” sections because of flooding and other poor conditions.

— Using the state of West Virginia’s subpoena authority, investigators are now going to subpoena everyone else they want to interview, after growing tired of some witnesses not showing up for scheduled appearances or repeatedly trying to reschedule. Investigators have been focused thus far on hourly workers from Upper Big Branch, but are now moving up into the mine management and corporate officials.

— In the hours after the April 5 explosion, MSHA officials had to order two Massey officials out of the mine … the company officials had gone underground without MSHA approval between the time that the explosion occurred and when MSHA took control of mine access. MSHA did not specify what those officials were believed to be doing underground.

— MSHA said it has no plans to try to counter the public relations offensive by Massey Energy with regular briefings to update the public and the press on the facts that are uncovered as the investigation proceeds.

You can listen for yourself to the call, as I’ve posted the audio here: