Census workers have found nearly 80,000 residents in three parts of the District who were missed in the first census count earlier this year, according to the mayor's office.

A Washington Post Sampling of those neigborhoods -- Adams-Morgan, Anacostia and Capitol Hill -- supports the contention that thousands of District residents may have been passed over.

The census Bureau's preliminary figures for the District showed a population of 568,300 which, if accurate, would mean a drop of nearly 200,000 people from the 1970 level.

City officials know that the District's population has dropped over the decade, but they believe the current figure should be closer to 640,000.

For the first time this year, the Census Bureau has presented localities with preliminary figures that they can attempt to refute. And in some cases, census workers will go back and review neighborhoods where an undercount is suspected.

City officials targeted Anacostia, Adams-Morgan and Capitol Hill as places where residents were missed for various reasons.

Census officials here would not confirm that they had found 80,000 additional District residents, but they said an undercount is likely because, according to Census Bureau address lists, only 76.9 percent of households in Southeast and Northeast Washington and only 81 percent of housholds on Northwest and Southwest returned the census forms that were mailed out in late March. Nationwide, 86 percent of household returned the forms, according to the census bureau.

If 80,000 people were missed, they represent about 12.5 percent of the people the District thinks it has.

Washington Post reporters went to the three neighborhoods and asked at random if residents had received and returned census forms and if not, if they had been contacted by census workers. Of the 89 families interviewed, 8 percent said they had not turned in a form and had not been contacted.

The percentage varied, depending on the neighborhood: 15 percent in Adams-Morgan, 10 percent in Anacostia and 6 percent on Capitol Hill. The figures are somewhat imprecise: Post reporters did not try a second time to contact those homes where no one was home, nor did they ask how many families or people lived in a home. In a few cases, people said another family member might have filled out the forms.

The Census Bureau is now conducting the second of two routine followup procedures in an attempt to find people not orginally counted. If the checks fail to bring the number closer to what the District expects, city officials said Mayor Marion Barry will request a recount.

Several cities, including Baltimore, have filed suit to get their census figures revised upward.

"It means a great deal to us that they [census workers] find the people," said Lillian Sedgwick, the mayor's special assistant and census coordinator. "I'm confident that they'll find all 100,000 missing people, probably even omore than that."

The numbers are critical because they can determine how much federal aid a city receivers. Officials estimate that each person can mean $200 in additional aid.

City Council member David Clarke (D-Ward 1), who represents the Adams-Morgan area, said he believes the census missed people there because Spanish-speaking residents who may be in this country illegally did not return the census forms, which ask for routine demographic data, including country of citizenship.

"Many people in my area don't want to be counted because of fears, albeit unjustified, that if the Census Bureau knows their whereabouts, it will lead to their deportation. And they don't want the Census Bureau knowing the whereabouts of their friends," said Clarke.

The Census Bureau does not provide specific census data by name or address to any other government agency.

Clarke said some Adams-Morgan residents may have received forms printed in English, which they could not read.

Interviews conducted by The Post with Spanish-Speaking residents there seemsed to confirm Clarke's observations.

Residents of two of the 19 households visited by The Post said they did not return the census forms and would not talk to census workers -- one because she was here illegally, the other becuse he had tax problems.

Others said they could not read the forms and did not return them, but they provided information to workers who visited them later on.

Maria Amparo Madrigal, who lives on Ontario Road, said she requested a form in Spanish, but never received it. However, she said a Spanish-speaking census worker later came to her apartment.

Anacostia residents may not have reported all the members of their housholds because they were violating leases or housing codes and feared they would be evicted, said Linda Moody, secretary of Advisory Neighborhood Commission 8A in Anacostia.

Two of the 20 families contacted by The Post in Anacostia said they did not received census forms and had not been visited.

"I heard a lot of people filled theirs out, but I never received one," said Joyce Robinson of Chester Street SE.

Moody sent a newsletter last week to 14,000 residents in Southeast, urging them to return census forms.

"It's crucial we have an accurate count in this area because so much of our housing is publicly provided and the funds for it will be cut if there is an undercount," Moody said.

Sedgwick would give no reason why the Capitol Hill area may have been undercounted. But there was a suggestion that some residents there may have been reluctant to open their doors to strangers.

Of 50 families interviewed on Capitol Hill, eight said they did not receive forms, and of that group, three said they were never contacted by a census worker.