Maria das Dores Celina, a nurse at the Josina Machel Hospital in central Luanda, told the Reuters news agency that two teenage girls had arrived dead at the hospital on Saturday.
"Their bodies were bruised. They were probably trampled as they rushed inside the stadium," she said.
One of the injured, Conceicao Cassange, 27, said: "There were just too many people inside the stadium and the temperatures were too high."
Security officials said police have launched an investigation.
'Clouds of evil'
Hundreds of thousands of people braved soaring temperatures again on Sunday to join the pope's open-air Mass.
|Angolans sat in 31C temperatures to attend the pope's Mass [AFP]
Benedict used the opportunity to urge Angolans to rebuild their nation after decades of civil war.
"Tragically, the clouds of evil have also overshadowed Africa, including this beloved nation of Angola," he said.
Africa has too often seen "the destructive power of civil strife, the descent into a maelstrom of hatred and revenge, the squandering of the efforts of generations of good people".
"It is to preach this message of forgiveness, hope and new life in Christ that I have come to Africa."
The pope is in Angola after visiting Cameroon on his first visit to the continent since taking over as pontiff. He will return to Rome on Monday.
More than 60 per cent of Angolans are believed to be Catholic - a religion introduced by Portuguese missionaries 500 years ago.
More than half of Angola's population is under 18, and many bear physical scars of the decades of fighting that has left the southern African country one of the most heavily landmined nations on the planet.