Last night marked the second time in less than a week that 25-year-old Debbie Voorhies had faced a crowd that surged toward her shouting and screaming.

The first time was in Islamabad, Pakistan, when a hostile mob of anti-American rioters swarmed over a wall to set fire to the apartment complex where Voorhies and other members of the U.S. Embassy families lived.

Last night Debbie Voorhies of Sterling Park, Va. was one of about 400 Americans evacuated from Pakistan who arrived at Dulles Airport to hear the warm welcoming shouts and cheers of friends, relatives and colleagues. h

When the evacuees, who had landed at 8:35 p.m. after flying from Pakistan via Europe aboard a chartered jumbo jet, finally arrived in the terminal, the building erupted in a pandemonium of joyous hugging, kissing and shouting reunions.

Voorhies' husband, Frank, also 25, and a State Department employee, was one of about 100 persons who had been trapped for hours in the top-floor code room of the embassy when rioters attacked.

Although he declined to comment on the ordeal there, his wife recalled vividly the sight of the mob scaling the wall to the apartment complex while she was alone at home with the couple's 3-year-old child, Jason.

Once within the walls, she said, the rioters "were throwing bricks through the windows and what sounded like cherry bombs." Amid the noise and confusion, she ran to the bathroom and locked herself and Jason inside.

Smelling smoke later and realizing that the building was ablaze, she crouched on the tile floor of the bathroom, rising periodically to scoop water from the toilet bowl, which she used to cool the child's face.

"I thought we were going to be killed," Voorhies told a reporter last night. "The people outside kept yelling they were going to kill us."

As it turned out, she and Jason spent a "very, very long time," six hours, on the bathroom floor before they were finally rescued.

When the order came to leave, Marianne Olson, of Burke, Va., took the family pictures from the wall, stuffed them in her suitcase, snatched up her two dogs and headed for the plane.

After the 24-hour flight from the Pakistani capital, the sight of her friends waiting in the Dulles terminal and the American flag flying outside were "the most beautiful thing I'd ever seen," she said.

Last night about 500 persons, many of whom had waited for hours, some carrying placards of greeting, were on hand to greet the evacuees at Dulles.

Those with area ties went to their own homes or those of relatives. Others were lodged at a nearby motel.

Among the arrivals were students from a school in Islamabad attended by children of embassy personnel. Greeted here by their friends and contemporaries, several recalled experiences that seemed to combine the terrifying with the matter-of-fact.

Pam Lassard, 12, of Tampa, Fla., remembered that her school day had just ended when students were informed by a teacher that a demonstration was under way in the area and they would have to stay after class.

Soon afterward, the girl said, she and her classmates were huddling in a corner of a classroom, as gangs of youths outside began throwing rocks and smashing windows.

Undersecretary of State David Newsom, who boarded the plane after it arrived at Dulles told the evacuees that "you and your loved ones and friends, whom you have left to carry on . . . the work of both the American government and private sector in Pakistan have our unqualified admiration and gratitude for the way you have responded."

About 70 persons were reportedly to be left in Pakistan to man the embassy and other U.S. government installations there.