Andersen's auditors were pressured by Enron's management to defer recognizing the charges from the special purpose entities as its credit risks became known. Since the entities would never return a profit, accounting guidelines required that Enron should take a write-off, where the value of the entity was removed from the balance sheet at a loss. To pressure Andersen into meeting earnings expectations, Enron would occasionally allow accounting companies Ernst & Young or PricewaterhouseCoopers to complete accounting tasks to create the illusion of hiring a new company to replace Andersen. Although Andersen was equipped with internal controls to protect against conflicted incentives of local partners, it failed to prevent conflict of interest. In one case, Andersen's Houston office, which performed the Enron audit, was able to overrule any critical reviews of Enron's accounting decisions by Andersen's Chicago partner. In addition, after news of SEC investigations of Enron were made public, Andersen would later shred several tons of relevant documents and delete nearly 30,000 e-mails and computer files, leading to accusations of a cover-up.