PORT-AU-PRINCE, Haiti (AP) _ A well informed medical source said Thursday that poison probably killed Jean-Claude Paul, the feared army colonel forced to retire after a coup in September.

''The cause of death is definitely not a heart attack,'' the reliable medical source told The Associated Press, speaking on condition of anonymity. ''The hypothesis that Paul was poisoned is highly probable.''

The source said Paul, 49, played soccer every day and was in excellent physical form and ''superb'' health. The source did not elaborate further.

Paul died Sunday and was buried Thursday outside his home in Fermathe, a wealthy hillside district.

Initial radio reports said he died of a heart attack, but family friends said he may have been poisoned and police sources called the death suspicious.

About 200 people, including family members and military officers, attended the funeral at Sacre Coeur Roman Catholic church in Port-au-Prince before a private burial at his residence, 10 miles east of the capital.

Paul's former wife, Mireille Delinois, his maid and gardener were arrested Monday and remained in custody Thursday at Petionville police headquarters with no charges filed.

Col. Georges Valcin, the police chief, said they would be held until an investigation of Paul's death is finished.

Antonio Paul, a brother of the colonel, has said Paul had convulsions and died in his arms an hour after drinking a bowl of soup. Remains of the soup were taken to a Miami laboratory for analysis.

An autopsy was performed Monday at the Morgue of the State University Hospital, but the results were not disclosed. Unidentified military sources quoted by radio stations said Thursday the findings would not be made public for at least a month.

In March, Paul was indicted by a grand jury in Miami on drug trafficking charges. Ms. Delinois, who was married to Paul twice and is the mother of his 13-year-old son, was arrested in Miami last year for drug possession and jumped bail.

Federal authorities sought to put Paul on trial, but the United States and Haiti have no extradition treaty.

Paul was commander of the 700-man Dessalines Battalion, the most brutal unit in Haiti's 7,000-man army, and was linked to the Tonton Macoutes, the dreaded private police under the 29-year Duvalier dictatorship.

Haiti's military leader, Lt. Gen. Prosper Avril, fired Paul on Sept. 30 in a purge of commanders who served under Lt. Gen. Henri Namphy. Avril replaced Namphy as president in a Sept. 17 coup led by army officers demanding democratic reforms and an end to violence.

Namphy came to power in February 1986 after Jean-Claude Duvalier fled into exile in France.