Guy Cantwell, a Transocean spokesman, said that they would not speculate but rather wait for all the facts before drawing a conclusion.
Eric Holder, the US attorney general, said that the justice department was taking part in an ongoing investigation into the spill.
"We are part of an ongoing monitoring [effort] and investigation along with our partners at DHS [the department of homeland security] and other agencies that are involved," Holder said.
However, a justice department official said that it was yet not a criminal probe.
Barack Obama, the US president, said on Sunday that his administration would require BP to bear all costs.
"BP is responsible for this leak; BP will be paying the bill," Obama said.
Meanwhile, Hayward said chemical dispersants seem to be having a significant impact in keeping oil from flowing to the surface.
The update on the dispersants came as BP was preparing a new, untested system nearly 1.6km under water to syphon away the geyser of crude.
However, the plan to lower 74-tonne, concrete and metal boxes being built to capture the oil will need at least another six to eight days to get it in place.
End not near
That could spill at least another 3.8 million litres into the Gulf, on top of the roughly 9.8 million litres already estimated to have spilled since the April 20 blast.
Officials were also trying to cap one of three leaks to make it easier to place the first box on the sea floor.
Crews continued to lay boom to try to keep the spill from reaching the shore, though choppy seas have made that difficult and rendered much of the equipment useless.
Fishermen from the mouth of the Mississippi River to the Florida Panhandle were informed that more than 17,612 square km of fishing areas were closed.
This was expected to have a devastating impact on their livelihood's for at more than the next 10 days, just as the prime spring season had begun.
The slick was also very close to a key shipping lane used to feed goods and materials to the interior of the US via the Mississippi River.
Even if the well is shut off in a week, officials say that it will take a long time for fishing and coastal life to return to normal.
Everything engineers have tried since the April 20 oil rig explosion has failed.
After the blast, which killed 11 people, the flow of oil should have been stopped by a blowout preventer, but the mechanism failed.
Efforts to remotely activate it have proven fruitless.
The oil could keep gushing for months until a second well can be dug to relieve pressure from the first.