WASHINGTON -LRB- CNN -RRB- -- First lady Michelle Obama 's father is not buried in the Chicago-area cemetery where investigators say hundreds of graves have been dug up in a scheme to resell the burial plots , a spokeswoman said Tuesday . First lady Michelle Obama 's father is not buried in the Chicago-area cemetery where graves were disturbed . The announcement followed an earlier , mistaken statement by the first lady 's communications director , Camille Johnston . Johnston later said that Obama 's father , Fraser Robinson III , was buried in Lincoln Cemetery in suburban Alsip , Illinois , not the Burr Oak graveyard now at the center of a criminal investigation . `` There has been some confusion that has been cleared up , '' Johnston said . Robinson , who worked as a pump operator for the Chicago water department , died in 1991 after a long struggle with multiple sclerosis . Lincoln Cemetery is about 2 miles from Burr Oak . Four people face felony charges in the investigation surrounding Burr Oak Cemetery in Alsip , Illinois . Authorities said last week that about 300 graves had been disturbed as part of the scheme , but that number is expected to rise . Cook County Sheriff Thomas Dart said his office has received more than 55,000 requests for information from families with loved ones buried in Burr Oak . But he said many of the cemetery 's records are in rusted cabinets filled with decaying file cards . `` Most of the file cards have rotted together , '' he said . `` They 're covered in mold , and they 've rotted together . '' In addition , some of the cemetery 's books are missing pages , and others are known to have been altered , `` So this has made it incredibly difficult for us to give accurate information , '' Dart said . His office asked a court Tuesday to appoint a receiver to manage the graveyard , which he said has been run by his office since last week . Among others buried in the 150-acre graveyard are civil rights martyr Emmett Till , blues pioneer Willie Dixon , jazz and blues singer Dinah Washington and several Negro League baseball players . Cemetery groundskeepers told investigators that Till 's grave was not among those disturbed , but the identities of other remains dug up have not been disclosed . Carolyn Towns , an office manager for the cemetery , and gravediggers Keith Nicks , Terrance Nicks and Maurice Daley have each been charged with dismembering a human body . The felony charge carries a sentence ranging from six to 30 years , authorities said . Authorities began investigating the cemetery about six weeks ago after receiving a call from its owners , who said they suspected `` financial irregularities '' regarding the business , Cook County Sheriff Thomas Dart told CNN last week . He said the owners are not believed to be involved in the alleged scam . CNN correspondents Dan Lothian and Elaine Quijano contributed to this report .