LOS ANGELES, Sept. 6 – A time bomb exploded in a sixth-floor washroom at the Hall of Justice in downtown Los Angeles Saturday, blowing a 9×11 foot hole in a wall and rupturing a six inch water main.

No one was injured in the explosion which occurred shortly before 1 a.m. and caused an estimated $10,000 damage.

The blast occurred about 35 feet down the hall from Dist. Atty. Evelle. J. Younger’s office and directly beneath the courtroom in which Charles Manson and three female codefendants are on trial for the Tate-LaBianca mass murders.

Younger said the bomb had been placed inside the washroom wall through a metal utility door used for access to pipes.

“All I know is that it had a timing device on it,” said Younger in describing the bomb. “It smelled like dynamite,” he continued, saying: “It could have been there a week.”

No fire resulted from the blast, but ruptured plumbing sent water cascading down stairwells, partially flooding the first six floors.

Sheriff’s deputies placed the building under tight security as workmen began repairing the damage and bomb squad experts attempted to reconstruct the explosive device from the few scattered remains that were found.

Nearly 3,000 persons were inside the 14-story building located at 211 W. Temple St., when the blast went off. The Hall of Justice houses offices of the sheriff, district attorney, coroner and public defender departments, as well as courtrooms and jail facilities for 2,800 county prisoners.

Two minutes after the explosion, a switchboard operator at the building received an anonymous telephone call that a bomb was set to go off in the building. The caller was a man.

At 2 p.m. Saturday a telephone caller told the Los Angeles Times a letter hidden in a Venice telephone booth contained an explanation of why the bomb was planted, officers said.

Times officials called police, who found the letter.

Defective Lt. Robert Helder, of the LAPD’s homicide division, termed the document a “crank letter.”

The bombing marked the second time within two months that explosives have been planted in the downtown area.

Police disarmed a timer-activated pipe bomb in the Los Angeles Times building 15 minutes before it was timed to go off July 26. The newspaper’s offices are located within walking distance of the Hall of Justice.

A bomb constructed of seven sticks of dynamite was dismantled at the California Highway Patrol’s Sante Fe Springs office Aug. 29.

Six units of Los Angeles city fire fighters were called to clean up the blast damage caused by Saturday’s bombing.

County jail inmates on the ninth through 13th floors, were awakened by the blast.

Dist. Atty. Younger said he had no idea if the bomb was aimed at him personally, but he had little doubt it was directed at his department, which occupies the entire sixth floor.

Younger, Republican candidate for state attorney general, said the bomb could have been planted for “a million reasons” by any of the 140,000 persons his office files charges against each year.

“If you get someone who’s unhappy enough, that hates enough or is sick enough to do a thing like this, then you just don’t know where to put the finger,” he said.

Younger refused to speculate whether the explosive had been left by any particular group or person, but called the device “obviously a time bomb.”

He said he smelled dynamite fumes upon arriving at his office shortly after the explosion.

Detectives found “some materials,” but not enough to quickly determine the composition of the bomb, Younger said.

The D.A. said security at the Hall of Justice would undergo “some changes” to prevent a recurrence of the incident, but noted additional security would be expensive and “an awful drain on manpower.”

A pile of red bricks and plaster lay in puddles of water in the restroom as firemen began mopping-up operations

By BILL HOMER