WASHINGTON (Reuters) - The results of a pivotal federal U.S. probe of last year's massive BP oil spill could be released as early as Wednesday, according to a source familiar with the matter.

The final report from U.S. Coast Guard and Bureau of Ocean Energy Management(BOEM) investigators has been heavily anticipated by investors eager for clues on possible legal ramifications BP and its partners may face from the drilling disaster.

The investigative team has declined to say when the report, which was initially supposed to be released earlier this year, will be issued.

But BOEM chief Michael Bromwich said Tuesday the team was in the "final stages" of completing its investigation and the release of the report was "imminent."

A source told Reuters that the report could be released some time Wednesday.

Last year's explosion on the BP-leased Deepwater Horizon rig killed 11 workers and spewed more than 4 million barrels of oil from the Macondo well into the sea.

The drilling disaster spurred a slew of investigations, lawsuits and regulatory reforms.

The Justice Department has already sued the well's owners, BP, Anadarko Petroleum Corp and Mitsui Co Ltd, as well as Transocean, the contractor that owned and operated the Deepwater Horizon rig.

More charges could be brought, however, and the findings from federal investigators could provide fodder for lawsuits that BP and its contractors have filed blaming each other for the biggest offshore oil spill in U.S. history.


Other official investigations of the spill have blamed the catastrophe on a series of mistakes made by BP and its partners.

Probes conducted by a presidential commission and the National Academies have said one pivotal mistake was the rig crew's decision to move ahead with the abandonment of the well despite tests that indicated problems with the well's integrity.

The presidential commission also blamed contractor Halliburton for faulty cementing on the well.

The Coast Guard also released a draft report in April citing serious safety lapses in the lead up to the accident by Transocean, which as the owner the oil rig, falls under the USCG's jurisdiction.

Both Halliburton and Transocean strongly dispute these findings, however.

Unlike some of the earlier probes, the report from the Coast Guard and BOEM will include findings about Macondo's blowout preventer, which was supposed act as a last line of defense against a major spill.

A forensic review commissioned by the federal team found that an off-center pipe stopped the device from operating properly.


In addition to the legal impacts of the federal report, the team's investigation may lead to further changes in the regulatory landscape for offshore drilling.

Following the Gulf spill, the government imposed a raft a new rules aimed at preventing another disaster and began a complete reorganization of the scandal-prone offshore drilling agency, which was then known as the Minerals Management Service.

The new rules, coupled with a temporary moratorium on deepwater oil exploration, slowed oil and gas development in the Gulf significantly.

Oil drilling activity is picking back up in the region, with 20 deepwater floaters drilling in area, up from 4 at this point last year, according to a Barclays Capital Research note.

Bromwich said the team's findings would help guide future regulatory efforts for his agency, but he does not anticipate the report will call for any immediate changes in drilling rules.

(Editing by Richard Chang)