A Chilean teacher held incommunicado for five days by security police on charges of subversion died Tuesday in a Santiago hospital, where he was being treated for wounds allegedly inflicted while he was jailed.

The human rights organization of the Chilean Roman Catholic Church demanded an immediate investigation yesterday, and the Interior Ministry announced its own probe.

The dead man, Frederico Alvarez Santibanez, 32, was among four persons accused last week of distributing subversive pamphlets and attempting to burn an unoccupied police van.

The security police -- the successor organization to the DINA, which was dissolved two years ago as part of an effort to improve Chile's police-state image abroad -- put the prisoner before a judge in such precarious condition that the judge ordered him hospitalized, court records show. They document, that the patient was suffering multiple contusions and hemorrhaging. His death early Tuesday was announced later that day.

Two women arrested last week along with Alverez were released by the court but the fourth prisoner, Raul Lopez Peralta, 20, is still in jail.

While arrests on political charges have dwindled in Chile in recent months, police surveillance is reported to have increased recently with the alleged return to Chile of the nephew of the late president, Salvador Allende. Andrews Pascal Allende is a leader of the underground Revolutionary Leftist Movement.

Sources in Santiago said newspapers there have been presenting convincing evidence that Allende has, indeed, returned to Chile.

The Chilean press, which has shown increasing signs of independence from the military rule during the past year, gave extensive coverage yesterday to the Alverez death.

In another development, U.S. sources indicated that the Chilean Supreme Court has asked new information on the American request for extradition of three officers charged in the death of exile Orlando Letelier. The court's decision -- expected this month -- now is unlikely at least until September, the sources said.