SAN FRANCISCO (MarketWatch) — The U.S. Coast Guard on Friday issued a potentially damning report on Transocean’s culpability in last year’s Deepwater Horizon disaster following a flurry of lawsuits this week.

The Coast Guard concluded that “deficiencies, and acts and omissions” on the part of Transocean RIG, -4.26% had an “adverse impact” on prevention and response efforts.

BP facing struggles

Those mistakes included poor maintenance of electrical equipment that may have led to the explosion, the bypassing of alerts and shutdown systems that could have prevented the blast, and having personnel who lacked the necessary training to handle the situation, the report found.

“These deficiencies indicate that Transocean’s failure to have an effective safety management system and instill a culture that emphasizes and ensures safety contributed to this disaster,” investigators said in the report.

The findings follow lawsuits filed by BP BP, -1.18% on Wednesday against Transocean, Halliburton Co. HAL, -0.16% and Cameron International Corp. CAM, +7.69% , three of the main contractors it worked with on the rig.

BP is suing Transocean for $40 billion, saying that its claims against the rig’s owner are consistent with the conclusions reached previously by the Presidential Commission.

Transocean fired back a day later with a lawsuit of its own, claiming BP had assumed full responsibility for the operation of the rig under its drilling contract.

Up to this point, BP has taken the biggest share of the blame, suffering more damage to its reputation than the others after the April 20, 2010 blowout on the Macondo field killed 11 rig workers and created the biggest offshore spill in U.S. history.