Three white men were arrested yesterday in Mobile, Ala., for the murder of a black teen-ager who was beaten, strangled, and hanged from a tree by a rope.

Police charged Ralph Hayes, 23, a pulpwood worker; Jimmy Edgar, 22, and his brother, Johnny Edgar, 26, with the murder of Michael Donald, a quiet, 19-year-old technical school student who was studying to be a brick mason. They are being held without bond in connection with the killing.

Donald disappeared Friday night around 11 p.m. after leaving his aunt's house in Mobile to buy a pack of cigarettes at a nearby service station. A passing motorist found him Saturday morning at 6 a.m., dangling from a nylon rope six to eight inches off the ground of a vacant lot in a racially mixed midtown neighborhood. A Mobile Man who saw the body on his way home from work, said Donald appeared to have been beaten; his clothes were caked with blood and streaked with dirt.

An autopsy revealed that Donald had been strangled with the rope, then hanged from the hardwood tree, police said. Witnesses at the scene told reporters that Donald's throat appeared to have been cut. The body was found across the street from an apartment complex where one of the three suspects lived. Sources said the men were at a party attended by blacks and whites the night before the killing. Police said they did not yet have a motive for the murder.

Mayor Robert Doyle said it is still unknown whether the crime was racially motivated.

But Dr. Robert Gilliard, president of the Mobile Chapter of the NAACP, said that, "whether he was black or white, this was a lynching."

Donald worked part-time in the mail room of the Mobile Press Register, the local newspaper, where fellow employes found him "quiet and introspective," said Henry Golott, the newspaper's night foreman.

"He tended to mind his own business, and kept to himself," Golott said.

Walter Blount, a teacher at Carver State Technical School, where Donald had been learning a trade since his graduation from Murphy High School, described the youth as a loner, "a good student, who had few friends." s

"So far, we don't know what happened," said one homicide detective. "But the victim appears to be as clean as any kid you would ever run across."

Police do not know how Donald came into contact with Hayes and the two Edgar brothers Friday night. Earlier he had been seen talking to people several blocks away from the party the suspects had attended. He frequently played basketball at the Spring Hill Avenue Recreation Center, less than one block from the vacant lot where his body was found, police said. But they said they have found nothing yet to indicate that Donald knew his alleged killers.

Police sources say two of the three suspects had prior arrest records.

The city of Mobile posted a $1,000 reward for the arrest and conviction of Donald's killer or killers.

The last documented lynching occurred in Poplarville, Miss., in 1959. Lynching generally is defined as a racially motivated killing -- most often by hanging -- that is perpetrated by three or more persons.