The Washington Post and The New York Times each won two Pulitzer Prizes in the 67th annual competition yesterday, and the Clarion-Ledger of Jackson, Miss., was awarded the public service prize for a series of reports on public schools.

Loretta Tofani of The Post's metropolitan news staff won the special local reporting prize for a series entitled "Rape in the County Jail" that detailed a pattern of sexual assaults in the Prince George's County Detention Center.

Loren Jenkins of The Post's foreign news staff won the international affairs reporting award for his coverage of the war in Lebanon and its aftermath, sharing it with Thomas L. Friedman of the Times, also honored for his reporting from Lebanon.

"It makes us very proud," Executive Editor Benjamin C. Bradlee said of The Post's two prizes.

The massacre at two Palestinian refugee camps in West Beirut also resulted in a Pulitzer in spot news photography for Associated Press photographer Bill Foley.

The 19 prizes for journalism and the arts, most of which carry $1,000 cash awards, were selected from a record field of 1,264 entries in a competition administered by Columbia University under the will of the late publisher Joseph Pulitzer. Other winners of the top journalism awards included The Boston Globe, which received the national affairs reporting award for a 56-page special Sunday section entitled "War and Peace in the Nuclear Age" and The News-Sentinel of Fort Wayne, Ind., for general local reporting about a devastating flood.

Also, The Miami Herald won the editorial writing category for its campaign against the Reagan administration's policy of detaining illegal Haitian immigrants, and Nan Robertson of The Times won the feature writing award for a personal account in The Times' magazine of how she was struck by toxic shock syndrome.

In the arts categories, syndicated columnist Russell Baker of The New York Times won the biography prize for "Growing Up," a personal reminiscence of his youth in Virginia's mountain country. Baker had won a Pulitzer in 1979 for commentary.

Alice Walker won the fiction prize for her novel "The Color Purple," a story of a teen-age bride in the rural South and her sister, a missionary in Africa. She is the first black woman to win the award for fiction.

Marsha Norman won the drama category for her play "'night, Mother," which deals with an elderly woman and her daughter who announces she is going to kill herself.

Susan Sheehan won the non-fiction category for "Is There No Place on Earth for Me?" a story of a paranoid schizophrenic who spent 17 years in institutions.

Rhys L. Isaac won the history award for "The Transformation of Virginia, 1740-1790;" Galway Kinnell won the poetry award for "Selected Poems," a distillation of 35 years of his work, and Ellen T. Zwilich became the first woman to win the music prize for her composition, "Three Movements for Orchestra."

In awarding the special local reporting prize to Tofani, the Pulitzer Prize Board noted that her series led to indictment of seven male prisoners on rape charges, the resignation of the county director of corrections and passage of $20 million bond issue to build a new jail. Since submission of the entry, five more men have been indicted.

Tofani, 30, was tipped to her investigation in a typically routine way: she was covering a sentencing hearing in the county courthouse when a lawyer for a young man about to be sentenced told the judge that his client had been "gang raped" in the detention center.

Over the next nine months, Tofani interviewed guards, judges, prison officials, perpetrators and victims. They told her that rapes occurred as often as a dozen times a week, that in many instances the victims had not been convicted of crimes and that poor jail conditions were to blame.

The three-part series included case studies of 12 rapes. In eight of the cases, the victims agreed to let Tofani use their names, "perhaps out of a sense of outrage over what had happened to them," she has since written.

She also interviewed 24 jail rapists, most of whom were convicted armed robbers and murders transferred from the jail to prisons elsewhere in Maryland. All but two of them described their crimes to her in on-the-record interviews, and some agreed to be photographed for the series.

Tofani said she thought she was able to get the interviews because "what seems so shocking to us is a normal part of life in prison for them."

In citing Jenkins, the Pulitzer board singled him out for his reporting "under deadline pressure" and for vivid eyewitness accounts of the immediate aftermath of the massacre in the Shatila refugee camp.

One such dispatch began: "The scene at the suddenly ghostly Shatila camp when foreign observers finally entered it this morning was a nightmare straight out of Dante. Women wailed over the deaths of neighbors and loved ones, bodies began to swell under the hot Levantine sun and the streets were littered with thousands of spent cartridges."

Jenkins, 44, a roving foreign correspondent who has reported on wars in Vietnam and Angola, said the siege of Beirut and the refugee camp massacres were "the ugliest stories I have ever covered."

He added that he felt a "sense of vindication" at receiving the Pulitzer. "The paper was getting a lot of flak about its coverage out of West Beirut," he said.

The Pulitzer awards were not without a touch of controversy, sparked by the decision of the board to transfer The Boston Globe's entry from the public service award category, in which it had been entered, to the national reporting category.

"The Pulitzer Prize Board again has underscored an unfortunate weakness in its procedures by selecting a winner that was never reviewed by the national reporting committee," said committee chairman Grant Dillman, vice president and Washington manager of United Press International.

"I do not quarrel with the merits of the winning Boston Globe entry," he said. "I have serious misgivings, however, about a procedure that lets a group of five top professionals, selected by the Pulitzer office itself, labor for three days to come up with three recommendations only to have the board select a winner switched from the public service category."

Thomas Kelly, director of photography for The Pottstown (Pa.) Mercury, said his panel on spot photography had selected Chester Panzer of WRC-TV in Washington as its top nominee for his photographs of the crash of an Air Florida jet and subsequent rescue attempts.

"We felt he had the best images on the table," Kelly said, recalling a photograph of a woman clinging to a life raft before being rescued. Kelly said still photographs made from Panzer's television footage were presented to the jury.

"We instructed the board at this juncture in the contest to decide whether or not television people should be in the contest. We had some heated go-rounds, and we felt next year's jury shouldn't have to go through this," Kelly said.

The board said that it has appointed a subcommittee to study whether television pictures later published in newspapers should be entered and will announce its decision before inviting nominations for next year's prizes.

Under the prize procedures, nominations of jurors in each category are only for the information of the board, which under terms of Pulitzer's will can accept or reject them or entertain an entry from a different category.

In the national reporting category, entries recommended by jurors were Haynes Johnson of The Post for articles on the impact of the recession around the country and Jim Henderson of the Dallas Times Herald for separate series on racism in the "New South" and on consequences of atomic testing.

The coveted public service award went to the Clarion-Ledger for a series of news articles and editorials dealing with a massive education reform package approved by the Mississippi legislature in a special 16-day session in December.

Winners in other journalism categories were:

* Editorial cartooning: Richard Locher of the Chicago Tribune for subjects ranging from President Reagan to the Middle East to home computers.

* Feature photography: James B. Dickman of the Dallas Times Herald for a special report on El Salvador.

* Commentary: Claude Sitton of the News & Observer of Raleigh, N.C., for his weekly column on national and international issues and regional politics.

* Criticism: Manuela Hoelterhoff of The Wall Street Journal for critiques of diverse subjects in the arts.