Fans were at the Olembe stadium in Yaounde on Monday (January 24) to watch the Africa Cup of Nations round of 16 game between the hosts and Comoros.
Images shared on social media, which could not be immediately authenticated, showed screaming fans being crushed at an entrance gate.
At a hospital next to the stadium, family members looked for their loved ones.
[Unidentified woman saying:] "All my family went to the stadium, afterwards I get a call to come to the hospital. When I arrived I find my big sister screaming, and my little brother is lying down here, a little further my nephew, I can't find the others."
New stadiums have been built for Africa's top soccer tournament.
But following low turnout in the first round of games, Cameroon's authorities have thrown open the gates, organized mass transportation and given out free tickets to lure fans.
The Confederation of African Football, the continent's top soccer governing body, said in a statement that it was investigating.
