Workers have dug up 18 bodies, apparently those of persons executed shortly after Chile's 1973 coup, Washington Post correspondent Charles A. Krause reported yesterday.

The bodies were found Tuesday in a nunmarked grave in Yumbel, a small village about 340 miles south of Santiago, after a court-assigned lawyer ordered part of the local cemetery excavated.

Sources close to the lawyer -- assigned by a civilian court in Concepcion to investigate the whereabouts of persons who "disappeared" after the coup -- said the corpses apparently belonged to 18 or 20 workers, professors, union leaders and leftist politicians who were detained in the Yumbel area shortly before the Sept. 11, 1973, coup that overthrew Salvador Allende and brought Gen. Augusto Pinochet to power.

If the bodies are identified positively as those on a list of missing persons maintained by the Catholic Church here, it would be the second time in less than a year that persons listed as missing were found dead in secret, mass graves.

Earlier this year, a military court ordered several national police officers detained after a civilian investigator determined that they were responsible for the deaths of 14 persons whose bodies were found last November in a mass grave near Lonquen.