WASHINGTON (CNN) -- Up to 80,000 items at the Ronald Reagan Presidential Library are unaccounted for, probably because of haphazard record-keeping and inventory procedures, officials said Thursday.



An audit found "significant breakdown in internal controls" at the Ronald Reagan Presidential Library.



An audit completed last month by the National Archives and Records Administration's inspector general looked at the management of presidential artifacts at six presidential libraries.



It "cites particular issues at the Ronald Reagan Library. ... We acknowledge that problems exist in inventory control at the Reagan library," said a statement from Allen Weinstein, national archivist.



Inspector General Paul Brachfield was more blunt.



A "significant breakdown in internal controls" was found at the Reagan library, in Simi Valley, California, he said in a statement Thursday.



The audit results prompted the Ronald Reagan Presidential Foundation to urge the National Archives -- which is responsible for maintaining the artifacts -- to move quickly to fix the problems.



The chairman of the board of trustees has contacted Weinstein "to express the serious concerns and disappointment on behalf of the Reagan Foundation and Mrs. Reagan," the foundation said.



Library officials told auditors that "the collection contained approximately 100,000 items, yet the library systems only had information to locate and account for approximately 20,000 items," Brachfield said.



"This does not automatically mean the approximately 80,000 remaining items are missing. The vast majority may very well be safely located within the library's storage facilities. ... Some of these items may be missing or stolen, or none of these items may be missing or stolen."



Control deficiencies at the library created an environment that could potentially have been exploited, Brachfield said.



Although Congress has a copy of the audit, it has not yet been made public because of the ongoing investigation into the whereabouts of the items.



The count of 100,000 was an estimate taken from the original Reagan White House Gift Unit database, Weinstein said Thursday, but was never meant to be used as a concrete inventory control number.



The Reagan library has already begun implementing recommendations from the audit, he said.



It has upgraded its management inventory software, is hiring additional trained museum staff, has begun a comprehensive inventory and is addressing storage issues by reshelving artifacts and taking steps to protect artifacts in case of an earthquake.



"Like all of the presidential libraries, the Reagan library stores their gifts in a locked vault, which is protected by a security camera," Weinstein said.



The audit examined management of artifacts at the Reagan library; the Franklin D. Roosevelt library; the John F. Kennedy library; the Gerald R. Ford library; the George Bush library; and the William J. Clinton library, Weinstein said.



"Early collections of artifacts came to presidential libraries with few controls and incomplete information relating to the collections," he said. E-mail to a friend
Which presidential foundation expressed concerns? Who expresses "serious concern"? Out of 100,000 items how many were recovered. Where are the items located? Who stated that this does not mean the remaining items are mising? What is the number of library items that library systems can locate? What foundation expressed "serious concerns"? Who said the items may be safely locked away? What is the number of items that library systems are able to locate?
Ronald Reagan The chairman of the board of trustees approximately 20,000 Ronald Reagan Presidential Library Inspector General Paul Brachfield 20,000 Ronald Reagan Presidential Weinstein 20,000
question: Which presidential foundation expressed concerns?, answer: Ronald Reagan | question: Who expresses "serious concern"?, answer: The chairman of the board of trustees | question: Out of 100,000 items how many were recovered., answer: approximately 20,000 | question: Where are the items located?, answer: Ronald Reagan Presidential Library | question: Who stated that this does not mean the remaining items are mising?, answer: Inspector General Paul Brachfield | question: What is the number of library items that library systems can locate?, answer: 20,000 | question: What foundation expressed "serious concerns"?, answer: Ronald Reagan Presidential | question: Who said the items may be safely locked away?, answer: Weinstein | question: What is the number of items that library systems are able to locate?, answer: 20,000