The Justice Department said Thursday an additional $64 million will be paid to victims of the spill, which spewed an estimated 4.9 million barrels of oil into the Gulf of Mexico. The spill resulted from an explosion that killed 11 Deepwater Horizon workers and scuttled the rig.
BP agreed to establish a $20 billion fund to compensate victims.
The underpayments were discovered in an independent audit of claims handled by Gulf Coast Claims Facility, The Hill reported.
"While there's no question that the independent GCCF labored under extremely challenging circumstances to get a huge number of payments processed successfully, the fact that this audit has resulted in tens of millions of dollars being made available to claimants who were wrongfully denied or shortchanged underscores the importance of the audit," acting Associate Attorney General Tony West said in a statement.
President Barack Obama appointed Kenneth Feinberg, who had overseen a compensation fund for victims of the Sept. 11, 2001, terrorist attacks, to manage the distribution of funds at GCCF. Gulf Coast lawmakers have criticized Feinberg and asserted compensation for BP spill victims was inadequate.
The fund distributed more than $6 billion to more than 220,000 recipients.
BP has announced it reached a definitive agreement that settles the bulk of the claims at an estimated cost of $7.8 billion.
"This settlement demonstrates BP's continued progress in resolving significant issues related to the Deepwater Horizon accident," BP Chief Executive Officer Bob Dudley said.