The eggs came flying out of the darkness on a walkway near their dorm at the University of Maryland and nearly hit her roommate. Days later, the young black woman who saw it happen said she is convinced the attack on her companion was racist.

"But she's white!" laughed a friend, hearing her tell the story over lunch at the student union.

"Yes," said the 18-year-old freshman, who declined to give her name, "but she was with me."

Stupid college prank? Or hate crime? It's hard to tell these days at College Park, where nerves are still on edge a week after several African American student leaders and officials received anonymous letters filled with racial slurs and threats of violence.

The still-unsolved mailings--and a troubling flurry of possible copycat incidents--have aroused tensions at Maryland's generally placid flagship college at a time when it has emerged as one of the nation's most diverse universities and won applause for its efforts to foster understanding.

In the past week, a comment interpreted as racist triggered a fistfight on a campus bus, students quarreled over plans for an escort service run by black students, and others have lashed out at the administration for alleged insensitivity toward the needs of ethnic minorities.

And while many black students believe the mailings are the act of an individual or a tiny group, they say the incident has reawakened them to the lingering existence of racial hatred--and left them wondering whether they're safe to walk alone on campus.

"There's a changed atmosphere," said Stephen Sutton, 27, a graduate student in computer science who is black. "People are more careful about what they say and what they do."

Such tension seems surprising on a campus that on the surface appears to be the model of the modern multicultural melting pot. Black and white students share lunch tables with Asians and Hispanics. Students in saris or veils mingle with others in bell-bottom jeans or baseball caps. Interracial couples hold hands, and passersby don't look twice.

Yet Maryland's diversity is a relatively new phenomenon. Segregated until 1954, the university didn't start admitting black students in significant numbers until the 1970s. Even so, the biggest changes have come only over the last 10 years, reflecting both the state's changing demographics and the university's concerted efforts to bring a greater variety of students onto campus.

In 1988, College Park's entering class of freshmen was 75 percent white. This fall, it was just less than 60 percent white. Black students, who made up about 7 percent of the class 20 years ago and just less than 10 percent a decade ago, now account for 14 percent of the class--numbers closely mirrored throughout the student body.

Meanwhile, Asian American students now account for 13.5 percent of freshmen, up from 1.5 percent 20 years ago and 8.6 percent a decade ago.

University officials point proudly to the demographics and say that U-Md.'s multiethnic blend has become one of its major selling points. A survey of African American students found that the school's diversity was one of the primary reasons they chose to enroll there.

"People tell us that this feels like a hospitable place," said Linda Clement, director of undergraduate admissions.

And administrators have worked earnestly to make the mix work. Students are required to take one of several dozen selected courses on diversity before they graduate, and instructors have been urged to include an awareness of other cultures in their course work. The university also has pressured the traditionally white social fraternities and sororities to diversify.

The campus had had its share of racial incidents over the years, officials said, including threatening e-mails that were sent to the editor of a black student newspaper this fall.

Yet they say no one can remember anything as brazen as last week's incident, in which letters filled with obscenities and misspellings arrived in the university mailboxes of the Afro-American Studies Program, the Black Student Union, that group's administrative officer and Student Government Association President Juliana Njoku, who is Nigerian.

One of the letters warned of the "coming of judgement day" and declared, "You will all die by the hands of the judge and jury."

University President C.D. Mote Jr. immediately denounced the mailings and organized a campus rally against bigotry, attended by several thousand students.

Yet in the ensuing days, with no one yet arrested for making the threats, tensions seem to have grown higher, and minor slights and misunderstandings have erupted into controversy.

The evening after the rally, a black female student called campus police to report that she was offended by the sight of a white man with black paint on his face. It turned out, police said, that the man was returning from playing a football game and had smeared anti-glare cream on his cheeks. Later, a fight erupted on a crowded campus shuttle bus after one passenger's request that some others move to the back was taken as racist.

"Everyone's on their tippy-toes," said Daryl Francis, 21, president of the Black Student Union, who found himself in the middle of one minor crisis last week.

A fellow Black Student Union member called a meeting to organize volunteers to escort students who felt intimidated by the racial threats. His comment that black students might not want white escorts was picked up by the student paper and denounced in a series of letters to the editor. Francis had to step in to clarify that the group would welcome all volunteers.

Yesterday, the Asian American Student Union sent out news releases denouncing a university administrator for not mentioning Asian Americans in his welcoming address at a conference about minority student retention last week.

The administrator could not be reached yesterday. Last week, he told the student newspaper that he hadn't mentioned Asians because they do not drop out in large numbers, as members of other minority groups do.

Students also have been shaken by a string of other incidents that have been reported to campus police over the last week, including a small number of threatening phone calls, slurs scrawled on a sidewalk and antisemitic comments written on envelopes found in the campus mail center.

Campus police would not say whether they think the incidents are connected. They say the increased number of such incidents may be attributable to a greater awareness in the wake of the letters to student leaders.

Most troubling to many students was an off-campus incident late last week. An 18-year-old black student driving on the Capital Beltway said she was accosted by men who shouted racist remarks from a passing car, then threw an object that shattered her window, injuring her slightly.

Though state police who are investigating the assault do not believe it is connected to the College Park cases, some students see an ominous trend. At the least, they say, one incident inspired the others.

"It's not a coincidence," said Njoku, the student government president. "I personally believe there is an organized group that feels that this is the time to make their presence known."

Some believe the tensions now racking College Park are inevitable. Jeffrey F. Milem, an assistant professor of education who has studied racial diversity in higher education, said that in any changing community, some members of the majority group begin to feel threatened when minority groups reach a certain level.

"It tends to create anxieties, particularly among students who haven't dealt with people across these lines," he said. Though College Park has dealt with its changing demographics better than most, "like any institution, it's going through growing pains."

Sarani Mukherji, an 18-year-old sophomore, witnessed some of those growing pains the day of the rally. Her English teacher preempted the regularly scheduled lecture in favor of a class round-table on race.

"At first, people were angry. They said, 'This is a diverse campus. How can this happen?' " But the students talked it through, she said, and decided that "we can't let this change anything."

CAPTION: U-Md. student leaders Juliana Njoku, facing camera, and Camille Adams hug during anti-racism rally called by President C.D. Mote Jr., right.