WASHINGTON — The causes of the massive Gulf oil spill will be laid out for the first time today by investigators for President Barack Obama’s independent commission, potentially shifting the blame and weighing in on disputes between companies over the largest offshore oil spill in U.S. history.

Representatives of the three companies most involved in the April accident — Halliburton, Transocean and BP — will be on hand to answer the allegations and respond to questions.

“It’s the first public look at the events and actions that our investigators believe contributed to the blowout,” said David Cohen, a spokesman for the seven-member commission, which has a Jan. 11 deadline to deliver a report to Obama outlining what caused the disaster and what needs to be done to prevent another one.