District of Columbia and federal authorities launched a formal investigation yesterday into allegations that thousands of dollars are missing from the personal bank accounts of residents at Forest Haven, the city's institution for the retarded.

Department of Human Services Director James A. Buford recommended the investigation after the city auditor's office spot-checked some of the patient accounts and found withdrawals of $12,000 to $15,000 unaccounted for in one transaction alone. Records of about 1,000 patient accounts -- which total some $500,000 -- were found to be "a shamlbes," according to sources close to the auditor's office.

Department of Human Services employes manage the private savings accounts of most of the almost 800 Forest Haven residents, who range from young children to the elderly. Many of the residents have accumulated substantial savings from earnings, inheritances and federal assistance payments.

"After the appropriate records are assembled and investigated, a determination will be made as to whether cash was withdrawn from residents' savings accounts and whether it was used for improper purposes," Buford said in a statement released yesterday.

The investigation is being conducted by the U.S. Park Police and the D.C. inspector general's office as well as Buford's own department. The Park Police are involved because Forest Haven, part of the city's sprawling Children's Center near Laurel is situated on federal park land.

City Auditor Matthew S. Watson's office began looking into records two weeks ago after receiving tips from a Forest Haven employe and a WRC-TV reporter that were passed on by a Senate Appropriations Committee staff member.

The auditors could find no accurate listing of the number of patient accounts in city records, or even whether the existing accounts belonged to patients who were still alive, according to informed sources.

In one instance some $2,000 was withdrawn last October from the account of a patient who had been dead for a year, according to these sources.

Buford acknowledged yesterday that there were "not enough checks and balances to provide better safeguards for the accounts." He said in his statement his department was "moving immediately" to correct deficiencies in the handling of residents' money.

Watson praised DHS last night for taking action. "This been a different attitude from what we're used to from Human Services," he said "For once a city agency has admitted a deficiency and is moving to correct it. This is healthy."

Auditors found that the official in charge of the business office at Forest Haven. Lenny Taylor, withdrew $20,000 from patient accounts at the Citizens National Bank in Laurel during the day's transactions last October, and that $12,000 to $15,000 of that is missing.

The money was supposed to be redeposited in a petty cash fund kept at Forest Haven so that residents could purchase specialized clothing, canteen goods and other items.

The auditors found no evidence that the money of six residents -- including one who died in 1978 -- was redeposited.

Taylor, who resigned from the Department of Human Services June 27, last night strenuously denied any wrongdoing during an interview with The Post.

"It's really been blowm out of proportion," he said. Taylor said records showing what he did with the money he withdrew are located in a locked drawer of a safe at Forest Haven. Buford said the employe with the keys to the drawer is on vacation and that the drawer would not be opened until her return on Monday.

Taylor voluntarily came to Buford's office yesterday morning to help locate records after watching an investigative report on the matter on WRC-TV (Channel 4) Wednesday night, according to Buford and Taylor.

"They can't reconcile the records. . . . My purpose is to help them," Taylor said last night. He said he resigned to take a job in Mississippi, for personal advancement "and not because money was missing."

His superior, acting DHS controller Roy Peters, yesterday described Taylor as "a loyal, dedicated employe." Taylor had been with the department for seven years and headed the Forest Haven finance office for the last three.

Peters said the patient accounts are audited periodically, but with no regularity. An audit in 1975 disclosed extensive "sloppy bookkeeping" and the handling of the patient savings accounts was transferred from Forest Haven counselors to his office, he said. Another audit in 1978 disclosed some "minor errors" but nothing of any substance, he said.

Peters said he believed there were between 500 and 600 savings accounts of Forest Haven residents at the Citizens National Bank branch in Laurel. oIn addition, some of the 200 former Forest Haven residents who now live in group homes in the District of Columbia have accounts at the Industrial Bank of Washington, he said.DHS officials yesterday were unsure exactly how much money was in these accounts. Peters said that he thought it was between $400,000 and $500,000 "but we're in the process of inventorying the whole thing."

To safeguard the savings accounts, Peters explained, two DHS employes -- each responsible to a different superior -- had to sign savings account withdrawal requests. In addition to Taylor, who reported to the controller, the other official was Willie Sims, who is chief of administrative services at Forest Haven.

Sims said yesterday that he routinely approved withdrawal requests and that Taylor then went to the bank to pick up the money. Sims said he never checked to see whether the money withdrawn was redeposited in patient accounts. He also said he has never been aware of any missing money.

Sources familiar with the audit review said that officials at the Laurel bank had become suspicious about large cash withdrawals from the accounts of mentally retarded people, and subsquently provided records of existing patient savings accounts that did not show up in Forest Haven records.

Bank officials yesterday refused comment.