Private researchers into the assassination of President Kennedy asserted yesterday that blowups of a long-ignored movie film may show two figures at the sixth-floor windows of the Texas School Book Depository about the seven minutes before the murder.

The blowups and portions of the film, taken 15 years ago by an amateur photographer named Charles L. Bronson, were shown to the press here yesterday under the aegis of the Assassination Information Bureau after their initial disclosure in the Sunday edition of the Dallas Morning News.

Robert L. Groden, a photo-optical technician who has served as a consultant for the House Assassinations Committee, said that in his opinion "there is more than one person" moving about the area where Lee Harvey Oswald is supposed to have set up his sniper's nest.

A sequence of greatly enlarged 8 milimeter slides of the double window from which the fatal shots were fired and of the first adjoining window several feet to the west seemed to show some objects shifting about at the same time, but it was not possible to make out what they were.

Groden maintained that "beyond question there is more than one person up there." He said computer enhancement of the images by the House committee might show just how many. He acknowledged the shapes were difficult to make out through the "very dirty" windows, but doubted they could be boxes that Oswald was moving about.

The Warren Commission said that another book depository employe, Bonnie Ray Williams, then 20, was also on the sixth floor shortly before the assassination, eating his lunch perhaps 20 to 30 feet from Oswald's perch, but said he saw no one and went down to the fifth floor where he joined two companions around 12:20 p.m. on Nov 22, 1963.

According to Groden, Bronson took his film of the crowd, including the book depository in the black, around 12:23 p.m. while waiting for the president's motorcade.

Grodon said the time could be fixed because an ambulance appears in the film. He said records compiled by the Warren Commission show the ambulance was summoned on an emergency call at 12:19 p.m., arrived at 12:22 and left at 12:24.

Kennedy was gunned down at 12:30 as his limousine was moving away from the depository. The Warren Commission concluded that Oswald, acting alone and hidden by cartons of books, fired the shots.

The FBI was informed of the Bronson film by a letter he wrote. Two agents viewed it with him and an Eastman Kodak representative on Nov. 25, 1969. But the FBI apparently concentrated only on subsequent segments, of the assassination itself.

Bronson also made some 35 mm shots with a still camera. FBI agent Milton L. Newsom discounted their value in a Nov. 25, 1963, memo, stating:

"These films failed to show the building from which the shots were fired. Film did depict the president's car at the precise time shots were fired; however, the pictures were not sufficiently clear for identification purposes."

Assassination Information bureau director Carl Oglesby, who said his nonprofit organization's research led to the unearthing of the film, chided the assassination committee for failing to discover it as part of its $5 million investigation. The AIB is pressing for continuation of the two-year House inquiry on the grounds that "more vital new information on the president's assassination is yet to come out."

The committee's chief counsel, Co. Robert Blakey, refused to comment beyond observing that Chairman Louis Stokes (D-Ohio) "has said repeatedly that this investigation ends Dec. 31." Committee staffers were expected to view the film last night. Bronson's lawyer, John Sigalas, refused to allow the press to take pictures of nay portions, partly, he said, to protect the value of his client's copywright.