WASHINGTON — BP, running weeks behind schedule and tens of millions of dollars over budget in trying to complete its troubled Macondo well in the Gulf of Mexico, took many shortcuts that contributed to the disastrous blowout and oil spill there last year, federal investigators concluded in a report released on Wednesday.

The central cause of the explosion aboard the Deepwater Horizon drilling rig was a failure of the cement at the base of the 18,000-foot-deep well that was supposed to contain oil and gas within the well bore. That led to a cascade of human and mechanical errors that allowed natural gas under tremendous pressure to shoot onto the drilling platform, causing an explosion and fire that killed 11 of the 126 crew members and caused an oil spill that took 87 days to get under control.

The two-part report, compiled by a joint task force of the Bureau of Ocean Energy Management, Regulation and Enforcement and the Coast Guard and covering more than 500 pages, is the most comprehensive to date on the April 2010 disaster. Its findings largely mirror those of other investigations, including the inquiry by a commission named by President Obama to determine the causes of the calamity. That panel issued its findings in January.

“The loss of life at the Macondo site on April 20, 2010, and the subsequent pollution of the Gulf of Mexico through the summer of 2010 were the result of poor risk management, last-minute changes to plans, failure to observe and respond to critical indicators, inadequate well control response and insufficient emergency bridge response training by companies and individuals responsible for drilling at the Macondo well and for the operation of the Deepwater Horizon,” the latest report said.