As we left for the weekend, the latest from BP about the situation in the Gulf seemed promising: For the first time since the disaster began in April, the flow of oil from the well had been stopped.

But it’s not over until it’s over for this so-called “nightmare well.”

Adm. Thad Allen, the national incident commander, had concerns about oil seepage from the capped well over the weekend, and those concerns were confirmed in a statement this morning. (Read Adm. Allen’s letter to BP requesting that more information be provided about oil seepage.)

“There were a number of unanswered questions about the monitoring systems they committed to as a condition of the US government extending the well integrity test,” Allen said. “Last night a conference call between the federal science team and BP representatives was convened to discuss some specific issues, including the detection of a seep near the well and the possible observation of methane over the well.”

Allen said BP must continue to monitor the seepage for signs of worsening, but in the meantime, the pressure test will continue for another 24 hours.

The Houston Chronicle’s energy blog noted that in a release posted last night, BP said the well’s pressure was measured at 6,792 pounds per square inch. BP had previously said that it hoped for well pressures of 8,000 to 9,000 pounds per square inch. 

Message boards, lawmakers and even Adm. Allen have for some time expressed concern that the well casing below the sea floor could itself be damaged, in which case rising pressure could make the rupture much worse.

McClatchy Newspapers pointed out that oil coming from damaged piping through the seafloor could also complicate plans for the relief wells:

BP currently hopes to seal the well permanently by intercepting it with a relief well. Heavy drilling mud would then be pumped into the Deepwater Horizon well, filling the well bore and drill pipe and stopping the oil from flowing by its sheer weight. A leak from the well bore through rock and to the seafloor, however, might defy such efforts.

It’s still unclear whether this new “seep near the well”—which was disclosed to journalists only last night—substantiates these earlier concerns, but it’s clear that officials are worried it might.