Human rights lawyers here charge that Chilean authorities have washed their hands of cases of missing persons after evidence pointed to government secret police involvement in illegal arrests and kidnapings.

Investigations ordered over the past year by the theorectically independent Chilean courts and reports promised by strongman President Gen. Augusto Pinochet had raised the hopes of relatives of about 500 missing persons, some of whom disappeared over three years ago.The organization, called Relatives of Missing Detainees, has made dozens of legal appeals for the missing and swamped the government, visiting digntaries and international human rights organizations with information on their cases.

A spokesman for the organization said Friday that the probe had been fruitless. None of the missing persons has been found or released and no criminal charges have been brought against secret police agents in cases in which the courts established that the missing were in their custody. The fate of the mising persons is one of the points the United States government has mentioned as a reason for its concern about human rights in Chile.

Twenty-six members of the missing persons organization staged a 10-day hunger strike earlies this year inside the offices of a United Nations agency here. The strike ended after the Pinochet government told U.N. Secretary General Kurt Waldheim it would provide information on the relatives of the 26. The organization said yesterday that in the two months since then, it has not received any information. U.N. officials in Santiago confirmed that there was "no news" on the government pledge.

In a letter last month to Pinochet, the missing persons organization said that in August, 1975 Pinochet had publicly ordered another investigation, that time of 119 cases, but that no report has ever been made public.

Human rights lawyers working, for the relatives of the missing persons said court investigations often establish secret police involvement but do not press charges. In one such case the Santiago appeals court ordered the government to release a young Communist leader, Carlos Contreres, after a regular police captain testified he witnessed Contreres' arrest in November, 1976 by four men who indentified themselves as agents of the secret police, then known as DINA.

The appeals court, shelved the case after receiving a letter from Pinochet ordering a military court to investigate. The letter was marked "secret" and addressed to a military court judge but included by the supreme court among the official document of the Contreres case. Pinochet said in the letter he was "concerned that the arbitrary arrest could have been carried out . . . by subversive elements."

In another case, Catholic University officials testified in early 1976 that DINA agents had made inquiries and said they were going to arrest education researcher Alejandro Avalos, a 30-year-old Communist. Avalos disappeared on his way to work in November, 1975. Other witnesses said they saw Avalos inside a secret DINA interrogation center.

The Chilean Supreme Court appointed special investigative judges with broad powers in two cases involving group arrests of eight persons in January, 1975 and 13 last December. An army regiment commander testifield that DINA agents held the eight for a time in his regiment headquarters near the port city of Valparaiso.

Human rights lawyers say none of the eight have been seen since their arrest and that the special investigation is at a standstill. The second case the 13 persons arrested in December and said to be members of the underground Communist Party, is still being investigated secretly by the special judge.The government has never admitted secret police involvement in any of the alleged arrests.

Several weeks ago, in a concession to Chile's human rights critics. Pinochet ordered the dissolution of DINA and replaced it by another internal intelligence organization without DINA's nearly unlimited power to arrest and hold suspects without charges or warrants.

The United Nations still has not received a report it requested from Chile on the mysterious death in July, 1976, of Carmelo Soria, an official of the Latin American Demographic Center, a Santiago-based U.N. agency Sori's family charged that the 54-year-old leftist had been under surveillance by secret police before his death.

A lawyer who helped coordinate the hundreds of missing person cases received by the Catholic Church's [WORD ILLEGIBLE] age of Solidarity, a human rights agency, complained that most investigations by Chilean courts were perfunctory and said investigators do not attempt to subpoena DINA agents whose identities the government keeps secret.

"The courts don't take the trou ble to conduct a thorough inquiry into the facts. Many cases are closed after DINA involvement in the kidnapping has been proved, but they shelve the cases before trying to find out the names of the guilty," he added.