Lawmakers say BP investigation uncovers new warning signs of problems

WASHINGTON (AP) — Two congressmen say that BP's internal investigation into the oil spill in the Gulf of Mexico has identified new warning signs of problems before the April 20 explosion that brought down the company's oil rig.

Reps. Henry Waxman and Bart Stupak say in a committee memo that the warning signs include an unexpected loss of fluid from a pipe known as a "riser" five hours before the explosion. That suggests there could have been a leak in the blowout preventer.

Engineers conducting tests on the system reduced the pressure to one of the lines to zero, while the pressure on the drill began to build. The memo says BP's investigator indicates that may have been a "fundamental mistake" because the rising pressure was an "indicator of a very large abnormality."