One person briefed on the inquiry said it was in an early stage and that no subpoenas had been issued yet to BP, the owner of the well. It was unclear whether any had gone to Transocean, which leased the Deepwater Horizon, the nine-year-old drilling rig that exploded and sank in April, to BP; Cameron, the company that manufactured a “blowout preventer” that failed to function after the explosion; or Halliburton, which performed drilling services like cementing.

Administration officials said they were reviewing violations of the Clean Water Act, which carries criminal and civil penalties and fines; the Oil Pollution Act of 1990, which can be used to hold parties responsible for cleanup costs; the Migratory Bird Treaty Act and the Endangered Species Act, which provide penalties for injury and death of wildlife.

“BP will cooperate with any inquiry that the Department of Justice undertakes, just as we are doing in response to the other inquiries that already are ongoing," the company said in a statement.

Having abandoned the attempt to plug the gushing well, BP and the government moved ahead on the latest plan, to contain the oil and gas as it flows from the floor of the gulf and siphon it to the surface. BP prepared to sever the pipe that once connected the well to the surface and is now snaking along the sea floor from the wellhead. That pipe, called a riser, had been attached to a blowout preventer, a stack of valves sitting on top of the well.

Removing the pipe could increase the flow of oil into the gulf until response crews can complete the next phase of the operation, affixing a cap to the remaining stub of the riser at the blowout preventer and siphoning the leaking oil into the cap through a new riser and up to a ship on the surface.