An MIT sophomore was injured yesterday afternoon when a pyrotechnic device, intended for use as a theater special effect, exploded in his hands before a crowded classroom.

The student, whose name was not released by Institute officials, was rushed to Massachusetts General Hospital.

The incident was part of a prank intended to promote a biannual Halloween party sponsored by the Phi Kappa Sigma fraternity, according to an MIT spokesperson.

Just after noon, a group of students, cloaked in Halloween costumes, entered an MIT lecture hall in a building known as Lobby 10.

The student who was injured intended to put the sparkling and smoking device in his backpack.

The plan was to promote attendance at the event--a party known as Skuffle that raises money for the Leukemia Society of America.

But the device exploded in the student's hands before he placed it in his backpack.

"He thought the device would add to the aura by going off in a puff of smoke," said Robert J. Sales, associate director of the MIT News Office.

An ambulance rushed the student, who suffered deep cuts to his hand, to a general emergency room just across the River. He remained at the hospital for observation last night.

Two other students who were standing nearby also suffered minor injuries. They were treated at MIT's infirmary and released.

Minutes after the explosion, the Cambridge Fire Department's hazardous materials squad arrived on the scene, along with the Cambridge Police Department's bomb squad.

One more device was found and diffused in the building, Sales said.

Lobby 10, located on Memorial Drive near Mass. Ave, was closed for an hour as MIT police investigated the incident.

At first, MIT officials and police did not know exactly what had happened, concluding only later that the device was not intended to be explosive.

"There are kits available that you can put together, that have a battery and a flash," Sales said. "It's not designed to explode."

Although the incident is still being investigated, it is unlikely that criminal charges will be filed, according to Cambridge police.

"It was an accident--a prank intended to distract and entertain," Sales said.