CAPE CANAVERAL, Fla. (AP) _ The first hint that something was terribly wrong with Challenger was missed by those in the viewing stands.

The words ''major malfunction'' that came over the public address system were drowned by cheering following the explosion that most took to be the separation of the shuttle's solid rocket boosters.

Tour guides had told many spectators earlier that the separation was a dramatic sight and an indication the shuttle would be on its way.

But word spread quickly that something was wrong.

The cheering stopped. The clapping stopped. The clicking of camera shutters stopped. Time seemed to stop.

''Where is the shuttle,'' a third-grader from Concord, N.H., asked as two zig-zag lines of smoke streamed out of the large smoke ball in the sky.

''Where is it?'' she asked again.

It was gone.

The next announcement from NASA on Tuesday, that the shuttle had exploded, caused a blast of emotion in the bleachers.

''Oh dear God in heaven,'' sobbed Mary Wuellenwebber of Concord, a parent- chaperone for a class of third-graders from Kimball School.

Schoolteacher Christa McAuliffe's son, Scott, 9, is a member of that class, but was not with his classmates for the launch. He was watching it with his father, Steven, and 6-year-old sister, Caroline, at another spot.

The space teacher's parents, Ed and Grace Corrigan of Framingham, Mass., stood a couple rows ahead of the youngsters with two of their adult children, Lisa and Christopher. They also didn't appear to comprehend the announcements that meant their daughter had vanished in a cloud of smoke and flame.

The Corrigans stood arm-in-arm as the rocket roared off the launch pad, and stayed that way as it climbed into the blue sky, then exploded.

The launch was emotional for Mrs. Corrigan, who was wiping tears from her eyes even as the announcement of a ''major malfunction'' was made.

They stood silently, calmly, during the agonizing seconds of silence.

A NASA official approached and said, ''The vehicle has exploded.'' Mrs. Corrigan, who last week said she was not concerned about her daughter's safety, repeated the horrible words as a question. The NASA official nodded his head to reaffirm the tragic news. The couple embraced and was led away.

The Concord children may not have known exactly what went wrong, but they knew something terrible had happened. Their teacher, their parents and many of the adults around them were crying.

They began crying, too. The tearful parents led them to their bus and someone rolled up their large ''Go Christa'' banner.

A few minutes earlier they had been counting down the seconds with the Mission Control voice that later brought the devastasting news that wiped the gleam from their faces.

Other stunned spectators walked away silently, many in pairs as though supporting each other.

The only words came in whispers, with a background of hollow-sounding footsteps on the metal bleacher steps.

It was as complete a shift of emotions as could be - and the shift came in the seconds that it took people to comprehend what they had seen.

Teacher Gordon Corbett of North Yarmouth, Maine, one of the 114 semi- finalists for the teacher-in-space spot, knew something was wrong when the two booster rockets kept going after the explosion.

''It took a few seconds to comprehend what was happening but that's all it took - a few seconds, and then just absolute horror knowing that ball of fire up there was not supposed to be there and hoping you'd see the shuttle come out of it and try for an emergency landing as they have been trained to do.''

Many of the people in the stands had extended their trips in Florida to see the launch. Its delays had forced most of the thousands of pupils, teachers, school administrators and other shuttle-watchers to leave.

Moments before the launch, Corbett said he was glad he had switched his flight plans. Someone who had seen launches told him they prompted ''emotions you never knew you had.''