The prisoners - Amer Tamba and Mudassar - misbehaved with a warden during a search of their cell on Thursday. The warden called in more personnel and thrashed them, the sources told PTI.
Following the incident, both men and some other death row prisoners went on hunger strike for a day.
A senior official of Kot Lakhpat Jail's administration told PTI that cell phones had been found in the possession of Tamba and Mudassar.
"The matter was handled according to jail laws and the prisoners did not go on hunger strike," the official claimed.
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Meanwhile, a judicial inquiry to ascertain how Tamba and Mudassar got possession of sharp edged "tools" to attack Sarabjit in April is underway but its findings are yet to come to light.
On May 2, Sarabjit succumbed to fatal head injuries allegedly inflicted by Tamba, Mudassar and some other prisoners.
The commission also issued notices to Sarabjit's relatives through the Foreign Ministry to record their statements and to produce any evidence they have regarding his death.
However, Sarabjit's family did not record their statements, the officials said.
Tamba and Mudassar, in their statements to the commission, confessed to the crime and said they killed Sarabjit as they wanted to avenge the killing of people in Lahore and Faisalabad in bomb blasts allegedly carried out by the Indian national.