A pre-dawn fire charred part of the Marine Classroom on the first floor of Shannon Hall--the ROTC building--yesterday morning. Officials suspect arson.

The fire was of "suspicious origin," Deputy Fire Chief John F. Kenney of the Cambridge Fire Department, who was in charge at the fire, said in his report.

Thomas J. Moriarty, head of the Naval ROTC unit at Harvard, went further. "I definitely think it was arson," he said. "There was very little damage," he added, and the only missing items were a few papers from the top of one desk. "They may have been used to start the fire," he said.

Cancer

On April 28, Robert H. Pell, head of Harvard's Army ROTC unit, received a mimeographed letter from "The Anti-War Establishment" which said, "a group of students has become so concerned with the cancer that exists in Shannon Hall that they believe the only recourse is to burn it out."

Pell's office promptly notified the University police, Dean Glimp's office, and the other ROTC units of the threat. Robert Tonis, Chief of University Police, had no comment on the letter. Archie C. Epps, assistant dean of Harvard College, said yesterday, "We did receive an unconfirmed rumor that something would happen to Shannon Hall. We considered it an unconfirmed rumor and did nothing about it."

According to Moriarty, a maintenance man on the third floor of the building heard the fire alarm go off at about 4:30 a.m. yesterday. He called the Harvard police, and then looked for the fire. He and the Cambridge police arrived at the site of the fire at approximately the same time.

Where There's Smoke

The sprinkler system had gone off at the same time as the alarm. When the men entered the room, there were no flames. Some furniture and papers were smoldering, and there was a lot of smoke. The policemen broke a window and threw charred maps, books, and a podium outside. Three fire engines, a ladder truck, and a rescue car arrived at 4:43 a.m. Moriarty said the police looked for fingerprints.

The damage is confined to one-forth of the classroom and consists primarily of charred furniture and papers, and soot on the ceiling. Water from the sprinklers soaked a rug next door.

Building and Grounds had not yet released its official estimate of damage yesterday.

"I think it was arson because one chair was piled on top of another, paper placed under them, and the fire started--that's not accidental," Moriarty said. He added, "This building is very, very easy to get into--all you need is a jackknife."

A spokesman for the Cambridge Police said that Harvard Police are handling the investigation. Tonis said that was wrong. He said "the Cambridge Police are conducting a very active investigation," and that his force is not taking part in it.

On the Other Hand

Lt. John R. Ambrogne of the state fire marshal's office is in charge of the investigation of the fire, according to the Cambridge Fire Department. Ambrogne said that he could use the help of any interested party, including the Cambridge police department.

"Any investigation would have to be approved by us," Epps said, "And we haven't ordered any investigation."

The maximum penalty for setting fire to an uninhabited building is 10 years in jail.