Clinton Foundation officials refiled five years of tax returns Monday after admitting to errors that covered up millions in government grants and foreign donations.

An examination of the charity's tax forms by reporters earlier this year prompted Clinton Foundation officials to undertake an "exhaustive review" of past returns, which uncovered "several additional errors," according to foundation president Donna Shalala.

In 2010, 2011 and 2012, for example, the Clinton Foundation did not list any government grants.

The amended tax form from 2010 included $8.8 million in government grants that was not previously listed.

Overall, the refiled tax returns revealed $20.1 million in government grants that were kept off the original versions of the forms.

The Clinton Foundation audit was performed by DLA Piper, a major donor to the same charity whose tax forms it examined.

According to the foundation's donor records, DLA Piper has given between $50,000 and $100,000 to the charity.

Other aspects of the tax returns were quietly updated to reflect additional, undisclosed contributions.

For example, the new 2011 return revealed $10 million in additional revenue that the Clinton Foundation did not originally report.

Contributions to the Clinton Foundation spiked last year as Hillary Clinton prepared to launch her campaign for president. The charity raked in $20 million more in donations last year than in 2013.

Shalala said the charity decided to refile four years of returns, on top of the 2014 return it filed Monday evening, due to the tax form's role "as a public disclosure document for our friends, supporters, partners, and the general public."