New Orleans, Louisiana (CNN) — The first part of BP’s “integrity” test on the new cap on its crippled oil well in the Gulf of Mexico is under way.

Senior Vice President Kent Wells says the middle ram of the three-ram stack on the new cap has closed. That’s an initial step in the process of testing pressure in the well. The move follows instructions from the U.S. government to proceed with the integrity test.

It’s hoped the tests will show whether the well, which has been spewing oil for 86 days, finally can be contained — either by closing the new 75-ton capping stack on the well or siphoning off oil to the surface.

The crucial pressure tests were put off Tuesday. But retired Adm. Thad Allen, who is heading the government’s response to the oil spill, said Wednesday that after intense consultations with Energy Secretary Steven Chu and other scientists involved, “At this time we’ll be releasing an order to BP to proceed with the well integrity test. But we gave them some additional direction to make sure we were are taking due care and in some cases an overabundance of caution, to make sure we didn’t do any irreversible harm to the well as we proceed.”

Allen said the officials “sat long and hard about delaying the test” and it was “not easy” to decide to delay. They want to make sure they’re “getting this right” for this “significant event,” he said.

A key question was whether shutting the well was worth the risk, or whether it might damage the well bore. Allen said the test will be a stop-and-go process.

The test — to check pressure in the well and determine if it can be sealed once and for all by the custom-designed cap — was had been expected to get under way Tuesday afternoon, but officials announced the delay late Tuesday night. The decision was made by the Deepwater Horizon Unified Command, which includes government agencies as well as BP. (FULL STORY)