When Angus Olsen, the director of Alexandria's supposedly impoverished housing authority, sat down at his desk one day earlier this month, he spotted something startling -- a check for $73,000.

It was in among the daily jungle of bills -- a check bearing the title "Chinquapin Investment Fund." That check, Olsen was to discover later, was only one of a series, now believed to total about $678,000, received by the housing authority and deposited by it in five separate bank accounts nearly every three months during the last decade.

The money apparently came from investments made with the proceeds of sales to the city government in 1967 and 1969 of same land owned by the authority, but it was virtually undetected by people who run the agency.

"For the last several years all we've heard is the housing authority board crying about how they didn't have the money to do anything," said City Council member Nelson E. Greene, who was a housing authority board member when the investments were made more than 10 years ago. "They couldn't afford to maintain the housing projects. All this crying. And now they're discovered nearly three-quarters of a million dollars."

Greene isn't the only city official demanding an answer. When informed of the discovery, the council Tuesday night directed City Manager Douglas C. Harman, who is Olsen's boss and technicaly heads the housing authority, to pursue an audit of the investment fund and discover how an agency that plagued the council as recently as two months ago with tales of financial woe could lose sight of nearly $700,000 when its yearly operating budget is barely three times that amount.

"While I don't think it's criminal," said council member Donald C. Casey, "I do think it demonstrates a lot of ineptitude, improper supervision and an unacceptable level of supervision by the housing authority board. The whole thing has made the city look quite foolish."

The man who city officials say could unravel the tale of the overlooked money has been unavailable for comment. He is Harland K. Heumann, the agency's former director, who was with the agency 29 years before resigning under pressure a year ago.

Without his comment, what emerges from the threads that the newly hired Olsen has been able to weave together and from conversations with people who worked with Heumann is as follows:

The discovery of the funds stunned both city and housing officials, but the fact that Heumann apparently never told anyone about them surprised no one. The deposits of money from two separate land sales in 1967 and 1969, they said, was an example of secrecy from a man who rarely told anybody anything.

"Heumann was a man who wanted it all -- power, everything," said Casey, describing the man who headed the agency from 1966 until he went on leave last March. "He was a man who wanted to do everything himself and who operated on the bureaucratic principle that the fewer people who knew something the easier it was to keep power.

"Heumann was an empire builder and that was what eventually forced him out."

After three years of battling with City Manager Harman and being fired and rehired, Heumann agreed to leave. He is on the housing authority's payroll until next month under terms of an agreement.

"I can categorically state that he [Heumann] never once mentioned the money. Not during a budget hearing, not during a board hearing. Not during any discussion. The [housing authority] board would ask for money to repair run-down housing units and he would just sit there and say there was no money.There were so many projects that needed money and never got done because he said he had no money," said Vola Lawson, head of the city's block grant program and acting director of the agency until January.

As recently as last month, completion of a major renewal project was delayed because of a lack of housing funds.

Housing authority staff members said they knew about the sale of some World War II-vintage public housing in the Chinquapin area to the city in 1967 and 1969, but never knew whether the money belonged to the agency, the city or the federal government.

Olsen said that in trying to trace the investment, he has discovered that the money from the sale was never included as a line item in the agency's annual budget -- only as a lump sum -- that slipped from the agency's budget logs in 1977. Housing officials familiar with the agency said a major reorganization of the agency in 1977 and the ensuing confusion could have caused the investment to go undetected during biannual audits. The five separate accounts were recorded separately in a ledger kept in the agency's vault.

The only person who knew about the ledger, according to Olsen, knew nothing about the accounts except that it was her job to enter the interest checks when they came in -- usually every three months. It was, Olsen said, only by chance that he traced the $73,000 check to that worker, who then escorted him to a vault and pointed to the ledger.