The Justice Department has decided to reopen a "limited investigation" into several aspects of the assassination of President Kennedy.

The renewed inquiry, recommended more than a year ago by the House Assassinations Committee, will focus on acoustical evidence that a second gunman had fired at the president when he was killed in Dallas' Dealey Plaza Nov. 22, 1963.

Robert L. Keuch, special counsel to Attorney General Benjamin R. Civiletti, said it was "also envisioned that several other investigative tasks" would be ordered as a result of the House committee's findings.

Rep. Louis Stokes (D-Ohio), who served as committee chairman, said he was gratified by the department's decision. Stokes said he also had been assured by Keuch that officials at Justice would undertake additional investigation into the 1968 murder of the Rev. Martin Luther King Jr.

Keuch could not be reached for comment, but a department spokesman said work on the King assassination was being restricted at present to a review by civil rights division lawyers of the House committee's voluminous reports.

Relying heavily on the acoustical evidence, the Assassinations Committee concluded in late 1978 that Kennedy "was probably assassinated as the result of a conspiracy." Committee experts said a long-ignored Dallas police tape of the sounds in Dealey Plaza showed "beyond a reasonable doubt" that a shot had been fired from the so-called "grassy knoll" in front of the president, in addition to those that came from the Texas School Book Depository behind him.

In the King case, the committee contended that there was substantial evidence of a St. Louis-based conspiracy that might have prompted James Earl Ray to murder the civil rights leader. Ray is serving a 99-year term in Tennessee state prison for the killing.

Keuch outlined the department's plans in the JFK case in a Dec. 12 letter to Stokes that the congressman made public yesterday. In it, Keuch apologized for the delay in responding to the committee's findings and recommendations, and blamed the delay on the department's "inability to obtain a complete copy of the committee's report."

The 28 volumes were made public last summer and have been on sale at the Government Printing Office since last July.

Keuch said he has asked the FBI to "conduct further limited investigation into several aspects of the assassination of President Kennedy," but he did not explain what these were.

As for the Dallas police tape, he said that the National Science Foundation's help will be sought in arranging an "independent scientific review" of the findings of the House committee's acoustical experts.

The Assassinations Committee also had asked the Justice Department to sponsor scientific examination of a film of the Dealey Plaza area just before Kennedy was shot.

Critics of the Warren Commission's original findings in 1964 that Lee Harvey Oswald was the lone assassin contended that the film showed evidence of two people at the windows of the book depository, Oswald's supposed perch.

Justice Department spokesman Robert Havel said officials were seeking to obtain the film, but he doubted that any further investigative work would be undertaken before the department verifies or rejects the acoustical evidence.

The House committee said it was satisfied that Oswald's shots killed Kennedy, but contended that Oswald was caught up in a conspiracy that may have been hatched by figures in organized crime.