(CNN) -- A Coast Guard report released Friday criticizes Transocean, the owner of the Gulf of Mexico rig that exploded a year ago, for serious flaws in its safety management system that contributed to the worst oil spill in U.S. history.
"There were serious safety management system failures and a poor safety culture that Transocean had," said Cmdr. Chris O'Neil, a Coast Guard spokesman, summarizing the investigation's findings.
The April 20, 2010, explosion on the Deepwater Horizon rig led to more than 200 million gallons of oil being released into the Gulf. Eleven people working on the rig died in the explosion, while another 16 were injured.
Besides the oil, hundreds of thousands of gallons of chemical dispersant went into the water as well. At the peak of the crisis, in June 2010, 37% of Gulf waters -- a total of 88,522 square miles -- were closed to fishing due to contamination.
The Coast Guard probe, one of several that delved into the incident, began six days after the incident and included seven hearings to compile information. The new report focuses on specific issues under that federal agency's purview. O'Neil said further conclusions will be released in the future.
"We didn't want to withhold what we had learned," he said, explaining that authorities thought it important to publicize "important recommendations that could be used to improve maritime safety" as soon as possible.
While noting that the events leading to the rig's sinking "were set into motion by the failure to prevent a well blowout," the report adds, "The investigation revealed numerous systems deficiencies, and acts and omissions by Transocean and its Deepwater Horizon crew that had an adverse impact on the ability to prevent or limit the magnitude of the disaster."
Specifically, the report claims that electrical equipment that might have ignited the explosion was poorly maintained and that gas alarms and automatic shutdown systems that might have prevented the blast were bypassed. In addition, on-hand personnel had insufficient training as to how and when to shut down engines and do other things that might have mitigated the disaster.
Besides Transocean, the probe also calls out the government of the Marshall Islands -- under whose flag the rig flew -- saying its "oversight and regulation of the Deepwater Horizon ... was ineffective." The republic delegated its inspections to "recognized organizations," the report says, without taking on the responsibilities itself.
In the 288-page report, investigators list 61 conclusions and offer 54 specific safety recommendations.
"We recognize that this report is important to a lot of people, particularly the families and friends of the 11 people who perished in the disaster," O'Neil said. "Nothing can bring those people back to us, but the investigation seeks to prevent a similar tragedy in the future."
Transocean did not respond immediately to requests for comment on this report. But on Thursday, Transocean issued a statement in which it blamed the oil company BP, which operated the oil well, for the disaster. This week, the two companies filed lawsuits against one another.
"The Deepwater Horizon was a world-class drilling rig manned by a top-flight crew that was put in jeopardy by BP ... through a series of cost-saving decisions that increased risk -- in some cases, severely," the Geneva, Switzerland, based company said in the statement. "BP set the stage for this disaster."
CNN's Melissa Gray contributed to this report.