BP officials told the House on Wednesday that the Deepwater Horizon oil well failed a key test on the morning of the April 20 explosion. The test revealed that gas had built up unevenly in the pipe; it’s now believed that a surge of gas caused the explosion. Separately, Representative Bart Stupak is expected to announce that the House has discovered “four significant problems” with the blowout preventer, including “a significant leak in a key hydraulic system.”