Warren Anderson, chairman of the board of Union Carbide Corp., was detained in a guest house here for six hours today in connection with the deaths of nearly 2,000 persons in Monday's poisonous gas leak at the Union Carbide-India Ltd. pesticide plant here, Indian officials said.

Anderson was released on the equivalent of $2,000 bail after being charged with criminal negligence and was flown in a government airplane to New Delhi with the understanding that he would be asked to leave the country immediately, Madhya Pradesh state information director Sudip Banerjee said at a news conference.

However, a spokesman for the U.S. Embassy in New Delhi who spoke with Anderson said, "The Union Carbide chairman did not consider himself under arrest or detained." The spokesman said by telephone from New Delhi that he understood there was a press conference in Bhopal in which charges against Anderson were listed, but he said Anderson made no mention of these charges or the surety bond that the state official said had been posted.

The official death toll in the disaster climbed today to 1,900 and is expected to go to 2,000, according to R.N. Tandon, chief medical officer of Bhopal. Tandon said the death rate was dropping daily, with only five deaths yesterday in the Jai Prakash hospital. Jai Prakash was the area hardest hit by the leak of the poisonous gas methyl isocyanate, used to make a pesticide..

But other medical officials here said they had seen new patients complaining of apparent delayed reactions to the gas.

The city's leading pathologist, Dr. Heresh Chandra, said new patients were still coming to his hospital and complaining of symptoms just developed five days after the accident, apparently in a delayed reaction, raising fears that the death toll may not have peaked. He cited one case in which an eight-month-old boy was brought into Hamidia hospital at 2 p.m. yesterday, having just developed shortness of breath, and was dead by 6 p.m.

Anderson was whisked out of a Union Carbide-India guest house and rushed out of Bhopal because "his presence might provoke strong passions against him and because we do not consider his presence in the city desirable," Banerjee said. He added that state authorities had asked the national government to see that the American left the country as soon as possible.

Arrested with Anderson were Keshav Mahendra, chairman of Union Carbide India, and its managing director, V.P. Gokhale, Banerjee said.

U.S.-based Union Carbide owns 50.9 percent of its Indian affiliate, according to the company's annual report. The other 49.1 percent is held in India.

The three senior executives were detained almost immediately after they arrived here by plane to investigate the causes of one of the worst chemical accidents in history. Two state police officers escorted the executives from an Indian Airlines plane to a waiting car and drove them to the company's spacious guest house several miles from the factory where they were held for a court appearance later in the day.

Banerjee said the arrests had been ordered by the state's chief minister, Arjun Singh, who was in nearby Indore campaigning with Indian Prime Minister Rajiv Gandhi.

Singh, in a statement read to reporters here by Banerjee, said, "We are convinced on the basis of facts already available that each of them has constructive and criminal liability for the events that have led to this great tragedy at the Union Carbide plant in Bhopal. This government cannot remain a helpless spectator to the tragedy and knows its duty toward thousands of innocent citizens whose lives have been so rudely and traumatically affected on the part of the management of Union Carbide."

When asked why Anderson was released and not Mahendra and Gokhale, Banerjee said it was because the two Indian executives had not asked for bail and because, "Mr. Anderson did not have any role in the day-to-day running of the factory." He said the two Indian executives were still in custody tonight.

Banerjee dismissed reporters' suggestions that the state government had come under pressure from the central government and indirectly from the U.S. government, saying, "There was no question of any consultation . . . . We did not not make any mistake, and we think we did this right." He stressed that the charges had not been withdrawn and that Anderson, "will be prosecuted."

The U.S. Embassy in New Delhi said Anderson's release was secured after delicate negotiations between the U.S. and Indian governments, United Press International reported. "The Indian government was very helpful," said William Miller, spokesman for the embassy.

White House spokesman Larry Speakes said in Washington that the United States had made "some representations through the embassy in New Delhi" but that he did not know if the U.S. action had prompted Anderson's release, The Associated Press reported.

A statement issued at the headquarters of Union Carbide in Danbury, Conn., said the incident violated a promise by the Indian central government to provide Anderson with safe passage, UPI reported. "Warren Anderson went to India fully expecting to be of assistance and was provided with safe passage assurances from the Indian government," the statement said.

The three executives were charged with seven offenses, including culpable homicide not constituting murder and causing death by negligence, Banerjee said.

Asked if he thought Anderson might simply not appear for trial, he said, "We have no reason to believe this will happen."

Anderson and the Indian executives were driven to the company guest house, where police refused to allow visitors, including James A. Becker, commercial consul of the U.S. Consulate in Bombay, who flew here with the executives.

Becker, who followed Anderson to the guest house in another car, said the arrest warrant was read to Anderson as he was being driven to the guest house. Becker said he first thought the executives were being given a VIP greeting until police slammed the gate at the guest house and refused to allow him to enter.

"If there had been any hint of being detained, our plans would have been changed. He came here to evaluate the facts and try to solve the problem, and he has been arrested," Becker said. He added, "We certainly felt from a U.S. government standpoint in India that they would not be arrested."

Banerjee said said Anderson was interrogated by police but not by officials of the central government. He added that he was not aware of any threats against Anderson's life, but added: "When there is public passion, whatever you think is possible is possible." Asked if that meant the state government could not guarantee Anderson's safety, Banerjee replied, "Yes, obviously."

Five officers of Union Carbide India, including the plant superintendent and works manager, were arrested shortly after the gas leak and charged with criminal negligence causing death.

As about 25 police guarded the gate of the luxurious guest house and research center today, Union Carbide India Ltd. research and development director V.P. Sriasto came to the gate and told reporters, "We were doing research work on the cause of the accident, but we can't do that because they won't let my scientists in today."

Becker said that after the arrest, two physicians, one from Union Carbide-India and one from the U.S. parent company's methyl isocyanate plant near Charleston, W.Va., were prevented from entering the guest house to pick up medical supplies to take to Bhopal hospitals, where 2,500 people are being treated for effects of the gas.

Meanwhile, Dr. Chandra sharply criticized Union Carbide India Ltd. for failing to turn over to doctors information about the leaked gas that, he said, could save lives.

Chandra said medical authorities had submitted repeated requests to the company for data on the composition and effects and possible antidotes of methyl isocyanate, but had received no response.

"Suppose you had those tanks here. isn't it your moral responsibility to tell us what was used, what is the treatment, what is the prevention? They have not come forward," Chandra said in an interview.

United Press International reported the following from Charleston, W. Va.:

A $15 billion suit was filed yesterday against Union Carbide, contending the giant chemical company was negligent in the design and operation of its plant in India.

The suit was filed in U.S. District Court on behalf of two families in Bhopal, but also asks that the case be named a class action on behalf of all victims of the gas leak disaster.