NEW ORLEANS — BP is temporarily letting oil pour out of a second pipe on its untested cap as part of preparations for closing all the valves to see how well it can contain the gusher.

The federal government's point man on the disaster, Thad Allen, said all the pipes might be closed later today. That would start a 48-hour experiment to see if the massive capping stack can stop the oil without blowing a new hole in the well.

BP late Wednesday shut down two of the three valves that control the flow of oil through the cap. But a leak discovered in a pipe overnight required a fix and the pipe was replaced early today. That sent BP back to the start of preparing for the test, including by reopening one of the two closed valves.