An air of unsettling calm enveloped the Islamic Center on Massachussetts Avenue yesterday as three gunmen continued to hold nine hostages there behind shuttered windows and drawn drapes.

Inside according to two hostages who were released late Wednesday and yesterday afternoon, the hostages sat in chairs quietly reading the Koran, the Moslem holy book, as the generally polite gunmen answered telephone calls or occasionally went to fetch bread and cheese from an apartment kitchen upstairs.

Police, many of whom lounged in full view of the shuttered windows waiting for something to happen, delivered food to a door on the front of the building at least twice during the day.

After a minute or so, the door would open, a hand would reach out to draw in the box or bag of food, and the door would shut. Some of the hostages inside were allowed to telephone or receive calls from family members.

Karl von Goetz, 30, a Maryland man who negotiated the release of his half-sister from the center yesterday morning, said he talked by phone with the gunmen and found them "very talkative and very cheerful."

Von Goetz said the gunmen told him that "there is no chance of anyone being harmed unless the police storm the building."

He said his half-sister, Cecile von Goetz. 48, a secretary at the center, told him that none of the hostages had been harmed, and that some apparently had slept Wednesday night, Lights in the area where the hostages were thought to be held in an area of offices in the front of the building went off at about 11 Wednesday night.

The atmosphere of calm at the Islamic Center set it apart from the more tense and more explosive situations at the District Building and B'nai B'rith headquarters as Washington entered its second day and night of terror yesterday.

There was one tense moment at the center Wednesday night, a police spokesman disclosed it, a press conference yesterday, when an apparent crank call was made to the gunmen by someone who told the gunmen that the police were about to "take action."

Police were able to smooth the situation over quickly, the spokesman said, by telephone contact with the gunmen.

The gunmen also maintained telephone contact with their apparent command headquarters at B'nai B'rith but when they did so they spoke in low and muffled voices so that the hostages in the center could not hear what they said, according to, Mushk Ara. a hostage who released Wednesday night.

Elements of reasonableness and even sympathy on the part of the gunmen seemed to play a role in the releases of Mrs. von Goetz and of Mushk Ara, 18, a student from Bangladesh who had begun working at the Center just a week ago.

A first Mrs. von Goetz's half-brother, who said he had been a mercenary soldier in Rhodesia, tried to exchanged himself for his hostage half-sister but was turned down.

Later, he said his half-sister was released on the "spur of the moment," and although he would disclose no further details he did say, "All I can say to the Hanafi Muslims is thank you a great big thank you."

Mrs. von Geotz was rushed to George Washington Hospital and then to a police command center for consultation. She could not be reached for comment.

She was later readmitted to the hospital with chest pains and placed in the coronary care unit, according to hospital officials.

Mushk Ara was released after her father, an employee of the Bangladesh Embassy, was forced by"fatherly feelings" to overcome his natural fear and telephone the gunmen.

"I telephone the mosque number," he said. "A gunman answered, I have him my customary Moslem greeting, Salaam Aleikhem, and started talking."

The father said he explained that he was a foreign national, as was his daughter, and that they had "nothing to do with local events." After some delays, another gunman told him, "You can take your daughter."

The daughtera reed-slim young woman, told a Washington Post reporter that she was busy praying to Allah much of her time in captivity while her companions consoled themselves reading the Koran.

She said the three gunmen, all black, wearing blue jeans and blue wool caps were "nice and didn't harm anybody."

She said the three gunmen had taken over the center's office and brought their hostages together, they ordered te men to remove their ties. With the ties and some additional rope they bound the men, except for one, hand and foot. They did not tie up the women, she said.

The unbound man was the center director, Dr. Muhammad Abdul Rauf. The young woman said that the gunmen specifically had asked where Rauf was shortly after they entered the building Wednesday.

Rauf had appeared and said, "What do you want?" and asked them who they were. One had answered, "We come every Friday for prayer." Then the gunmen told Rauf to go in a corner with the others.

After binding the men, the gunmen then split the group in two with half in Dr. Rauf's office with one gunman and the others in his secretary's office with the other gunmen.

The gunmen, who had already turned on the radio to get the news, then provided chairs for everyone and prepared to sit out the siege, the young woman said.

She said the hostages were allowed to talk to each other, but only in English, and there was little conversation.The hostages initially turned down offers of food made by the gunmen, she said, but later Wednesday evening they accepted. One gunman went for aging in Rauf's apartment above the office where the hostages were being held.

She said the entire incident began about 11 a.m. Wednesday when "a man walked into the room where I was working. He had a shotgun in his hands and two big knives at his sides."

As Jusk fell last night, seven men and two women included Rauf's wife. According to unofficial tallies, there were five Egyptains, two Americans, a Turk and a Columbian being held - employees of the center, visitors and tourists.

It was still not entirely clear yesterday why the Hanafi Muslims had targeted the center, located at2551 Massachusetts Ave. NW and whcih has long been a center for Muslim religious and cultural activity.

It was targeted to make an "international incident" that would point out the threat to the Islamic faith of the "Cassius X. Clay Gang," known as the Black Muslim sect, said Abdul Aziz, the son-in-law of Hanafi patriarch Hamaas Abdul Khaalis, in an interview yesterday.

Aziz, who did not participate in the hostage-talking with Khaalis and other Hanafis, has been an outside spokesman for the Hanafis during the reign of terror. He appeared once at the food to the front door.

Edmond Howar, treasurer of the center foundation, said Dr. Rauf has "been supportive of the changes in the Black Muslim movement since it turned away from black supremacy and moved toward a more traditional view of Islam."

He said that Rauf has met with Black Muslim leaders to exchange ideas and that the center has shipped more than 6,000 copies of the Koran to Black Muslims in Chicago.

Howar said boxer Muhammad Ali (formerly Cassius Clay) prayed at the center within the past few months and was photographed there.

Deputy Police Chief Maurice T. Turner said in a press conference near the center yesterday that the food delivered to the center included eggs, bananas, apples and dates all costing no more than $20.

He said that both the release of hostages and delivery of food resulted from "a dialogue that has been going on all morning." He said he conducted the dialogue himself by telephone and that the gunman he talked to inside was "clam and in control of himself."