So much for BP’s plans to cut off the flow of oil with its newly-installed cap on Tuesday.

It appears that the US administration, in the form of energy secretary Steven Chu and USGS director Marcia McNutt, has stepped in and demanded more analysis before the valves are shut off.

From incident commander Admiral Thad Allen:

“Today I met with Secretary Chu, Marcia McNutt and other scientists and geologists as well as officials from BP and other industry representatives as we continue to prepare and review protocols for the well integrity test – including the seismic mapping run that was made around the well site this morning. As a result of these discussions, we decided that the process may benefit from additional analysis that will be performed tonight and tomorrow.”

So what could Chu and McNutt et al’s concern be?

The plan was to shut the valves off for between six and 48 hours, giving BP time to monitor well pressure. Consistently high pressure, of about 8,000 – 9,000 pounds per square inch, would indicate the well casing was intact. Lower or inconsistent pressure might mean that oil and gas were escaping from other places below the sea bed; the cap risked further rupturing the well in ways that would be very difficult to fix.

In otherwords, the cap is being tested to see if it’s safe to use again in the future.

So perhaps the fear from the administration it is that shutting the valves off completely, even for a test of several hours, would actually threaten the well casing.