Justice Mazahar Ali Akbar Naqvi, the head of the commission, collected the complete record of Sarabjit from prison officials.
Registrar Bushra Zaman of the High Court told reporters that the commission had interviewed some prisoners about the incident and gathered complete records of the case.
The commission had already issued notices to Sarabjit's family through the Foreign Ministry to record their statements and produce any evidence they had regarding the incident, Zaman said.
Local witnesses have been summoned on June 10 to record their statements. The commission will unearth the facts at the earliest in view of the importance of the matter, she said.
The commission will also interview the two prisoners arrested for attacking Sarabjit, jail officials and witnesses before finalising its report.
Five to six prisoners had brutally assaulted Sarabjit in a well-coordinated attack on April 26.
After being comatose for nearly a week, Singh died at Jinnah Hospital in Lahore on May 2.
Police registered a murder case against two death row prisoners Amer Aftab and Mudassar for allegedly assaulting Sarabjit.
Both men told police that they wanted to kill Sarabjit as he was involved in killing Pakistanis in bomb blasts.