NEW ORLEANS – Officials are conducting a series of tests of BP’s broken oil well in the Gulf of Mexico to determine whether a “temporary” seal installed a month ago has plugged the well for good.

A final decision was expected today on whether crews need to go ahead with drilling relief wells for a so-called “bottom kill,” in which mud and cement are pumped deep underground to permanently seal the well.

Retired Coast Guard Adm. Thad Allen, the Obama administration’s point man on the oil spill, said at a news conference Thursday that an earlier effort to temporarily plug the well might have unexpectedly created a permanent seal.

However, he cautioned, it’s more likely that drilling will continue on two relief wells, which have been said to be the only way to ensure the blown-out well doesn’t leak again. That work has been delayed because of bad weather and wouldn’t resume for about another four days, if testing shows it’s needed.

Last month, after a cap meant to be temporary was fitted on top of the broken well and halted the oil flow, crews pumped in mud and cement from above in a so-called “static kill.” Some of the cement may have gone down into the reservoir, come back up and plugged the space between the inner piping and the outer casing — which is what engineers were hoping to do with the bottom kill, Allen said.

“A bottom kill finishes this well. The question is whether it’s already been done with the static kill,” he said.

Officials are testing pressure levels in that space between the inner piping and outer casing. Rising pressure means the bottom kill is still necessary, Allen said. Steady pressure could mean cement already has plugged that space.

But Allen said tests won’t show how much cement is in the space, making the original plan for a bottom kill a better way to ensure a permanent seal.