NEW YORK (CNNMoney.com) - American International Group Inc. agreed to pay more than $1.6 billion to settle claims related to improper accounting, bid rigging and practices involving workers' compensation funds, regulators said Thursday, making it the biggest regulatory settlement by a single company in U.S. history, according to Reuters.

Under the agreements, AIG also acknowledged misconduct and adopted a series of reforms. The Securities and Exchange Commission announced the settlement in coordination with New York State attorney general Eliot Spitzer, as well as the Superintendent of Insurance of the State of New York and the Department of Justice.

"AIG was and is a solid company that didn't need to cheat," Attorney General Eliot Spitzer said in a statement. "It finds itself in this position solely because some senior managers thought it was acceptable to deceive the investing public and regulators. However, by changing management, implementing reforms and providing restitution to injured investors, customers and states, the company has placed itself on a path toward resurgence."

In an interview in New York City, the attorney general made a point of saying the new management at AIG has done a "spectacular" job cooperating with the investigation and putting in reforms, according to Reuters.

"These settlements are a major step forward in resolving the legal and regulatory issues facing AIG," AIG President and CEO Martin Sullivan said in a statement. "We have already implemented a wide range of improvements in our accounting, financial reporting and corporate governance, and will continue to make enhancements in these areas. AIG is committed to business practices that provide transparency and fairness in the insurance markets."

In early 2005, the Attorney General, the Insurance Department and the SEC began jointly investigating a series of allegedly fraudulent transactions between AIG and General Re in 2000 that investigators have said improperly pumped up AIG's books by $500 million.

The New York-based insurer misstated its financial results through sham transactions created for the purpose of misleading the investing public, the SEC said in its complaint.

The settlement does not resolve the pending case against AIG's former chairman and CEO, Maurice "Hank" Greenberg, and its former chief financial officer, Howard Smith.

"There are some who continue to deny there was any wrongdoing at the company," Spitzer told Reuters, "I think the facts laid out today are overwhelming in establishing that from the highest levels of AIG there was an intent to misrepresent the financial condition of the company."

"While this settlement concludes our investigation of AIG, our investigation continues with respect to others who may have participated in AIG's securities laws violations," said Linda Chatman Thomsen, director of the SEC's Division of Enforcement.

Separately, AIG settled a federal lawsuit in which it accused two former executives of using confidential information from its computers to help start a rival firm, but the terms were kept confidential, according to Reuters.

AIG had sued Peter Yu, a former chief executive of its AIG Capital Partners Inc. private equity arm, and William Jarosz, the unit's general counsel.

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Some former AIG execs face fraud charges. Click here.