The body of a retired 53-year-old Washington high school teacher and investor who had been bound and gagged was found floating near Baltimore's Inner Harbor yesterday, six days after he had been reported missing.

The victim, whose body was recovered from the Patapsco River, was identified as Armand Labat. Baltimore police described his death as a homicide, but said there was no immediate indicaton of who killed him or why.

Labat, who reportedly had substantial investments and was a member of a family prominent in the D.C. school system, was last seen Tuesday moving items from a house he was selling on Argyle Terrace NW.

He was reported missing on Wednesday and his case was classified as "critical" after he failed on Saturday to appear at settlement for the house at 3831 Argyle Terr.

A 1980 real estate directory lists him as part owner of the house, which was assessed at $128,847. Police listed Labat's own address as 1819 Quincy St. NW. According to the directory, Labat was sole owner of that house, which was assessed at $185,781.

The victim's sister-in-law, Margaret Labat, an assistant D.C. school superintendent for communications and public relations, said in an interview that she could offer no explanation for Labat's disappearance.

She said that she knew of no threats against his life and that he was not known to carry large sums of cash, terming such a practice "most unlike him."

The victim's auto was found in Washington and taken to police headquarters for examination.

Mrs. Labat said she "couldn't think of any reason why" anyone would wish to harm her brother-in-law.

Labat was a graduate of Dunbar High School and Howard University, and earned a master's degree from Indiana University.

Described by his sister-in-law as a teacher of Spanish who had retired from Roosevelt High School, Labat in 1956 was awarded a Fulbright teaching grant to lecture at a college in Baghdad, Iraq, on the teaching of English as a second language.

Labat's brother Joseph, husband of Margaret Labat and a teacher in the D.C. public schools, was killed in a 1967 boating accident on Chesapeake Bay.