In his testimony before Congress this morning, Douglas H. Brown, chief mechanic for the Deepwater Horizon oil rig, recounted a dispute between a BP official and Transocean crew members that took place the day of the rig's explosion. At issue was whether BP could replace heavy drilling fluid -- typically used in the final stages of plugging oil wells -- with a lighter liquid, a substitution crew members appear to have opposed.

"The driller was outlining what would be taking place, whereupon the company man stood up and said, 'No, we'll be having some changes to that'...The OIM, tool-pusher and driller disagreed with that, but the company man said, 'Well, this is how it's gonna be.'"