Two ex-policemen who were convicted in local court of killing a Mexican-American prisoner, but who received sentences of one year in prison and $2,000 in fines which were then suspended, were indicted today on federal civil rights charges that could bring them life imprisonment.

In addition, a federal grand jury here indicted two other former Houston city policemen on charges of violating the civil rights of Joe Campos Torres. The four indicted ex-policemen allegedly ganged up on the prisoner and beat him before one threw him into a Houston bayou while another allegedly said "this would be a good time" to see if "the wetback" could swim. Torres drowned.

Today's indictments were hailed in the Mexican-American community as putting southwestern law enforcement officials on notice, as southern officials were a decade ago, that they may face federal action if local law enforcement fails to protect the rights of minorities.

The indictments reflected a Carter administration directive reversing an Eisenhower administration ban on federal prosecutions for civil rights violations on which state action had been taken.

The directive was issued specifically to bring about prosecution of another Texas law enforcement official who is accused of killing a Mexican-American prisoner. And, another death of Mexican-American while in custody in Texas is under review by the Justice Department.

Today's indictments came as no surprise. After ex-officers Terry W. Denson and Stephen Orlando, who had been charged with murder, were convicted of negligent homicide, a misdemeandor, and their punishment suspended, the protest began. Even the city's police chief denounced a "tragic miscarriage of justice."

Gov. Dolph Brisco, Attorney General John Hill, U.S. Sen. Lloyd Bentsen (D-Tex.) representatives of a state that traditionally treasures state's rights as much as oil, all had called for federal action.

Denson, Orlando, Joseph J. Janish, and Louis G. Kinney were charged with conspiring to injure and intimidate Torres - depriving him of his constitutional rights and resulting in his death. Conviction on that charge carries a maximum of life imprisonment.

A fifth officer, Glenn L. Brinkmeyer, was named an unindicted co-conspirator and was charged separately in a criminal information. Brinkmeyer testified under immunity against his fellow officers at the state trial. He testified in state court, too, that he had agreed with federal investigators to accept a one-year probationary sentence in exchange for his testimony in the federal charges, according to lawyers.

Other counts of the indictment charged deprivation of Torres' rights and that Denson, aided by Orlando, Kinney and Jannish, pushed Torres into Buffalo Bayou last May 6 where Torres drowned.

The final court alleged that Denson, Kiney and Orlando conspired with Brinkmeyer to obstruct justice by urging another policeman to misrepresent the facts of Torres' death to an FBI agent.

"We have to express our gratification with the indictment," said Reuben Bonilla, a Corpus Christsi lawyers who is state director of the League of United Latin American citizens. "I have faith the evidence will warrant a finding of quilty with appropriate prison sentences commensurate with the atrocious crime committed."

Bonilla praised U.S. Attorney General Griffin B. Bell for modifying the Eisenhower-era policy that barred a federal prosecution following state court actions. The change affects only civil rights cases, and the U.S. Supreme Court has upheld the legality of second prosecutions.

Last month, Frank Hayes, a former Castroville, Tex., town marshal was convicted of violating the civil rights of Richard Morales, with Morales dying, in a 1975 shooting. It was that case that prompted Bell to change the Justice Department policy: a state court had convicted Hayes of aggravated assault and sentenced him to two to ten years. He now faces a maximum on the federal conviction of life imprisonment.