Investigators of the Cambridge on Accelerator explosion may ready to report on its probable within two or three weeks.

J. Rizzo, chairman of the Energy Commission team, yesterday that the group is close "a possible sequence of " for the July 5 blast. It is now that the explosion originated in the immediate area of the bubble chamber or in one of systems nearby that inflammable gas, he said. early-morning explosion at the , which is operated jointly Harvard and M.I.T., injured 7 and killed a 19-year-old technology At the time of the blast, the chamber was in the final stages of a program for cooling it and filling it with liquid hydrogen that was being tried for the first time.

According to Rizzo, it is likely that the team will recommend some structural and procedural changes in the CEA experimental hall. M. Stanley Livingston, CEA director, said yesterday that some minor changes -- including a different fire alarm system and additional passages from the center of the hall to the outside -- have already been included in plans for the $1 million reconstruction job.

Scientists will probably be able to resume work in the hall around Nov. 1, Livingston said.

But the staff of a laboratory in Hamburg, Germany, has offered to perform experiments for Harvard and M.I.T. scientists while the hall is being rebuilt, Karl Strauch, professor of Physics, told the Summer News yesterday.

The laboratory, the D.E.S.Y., has a bubble chamber that is almost the duplicate of the CEA's -- the only duplicate in the world, Strauch explained. "We're seriously considering the offer and it's very much appreciated," he said.