A valley dam that authorities in Rwanda say could contain about 30,000 bodies has been discovered more than a quarter-century after the country’s genocide in which 800,000 ethnic Tutsi and Hutus who tried to protect them were killed.

The discovery is being called the most significant in years, and 50 bodies have been exhumed so far in efforts that are challenged by the East African nation’s coronavirus-related lockdown.

Rwanda on Tuesday marks the 26th anniversary of the genocide, but because of the lockdown, the country will follow events on television and social media as gatherings are banned.

Word of the valley dam and the bodies it held emerged as many people convicted in the genocide are being released from prison after serving their sentences and offering new information on mass graves. Other information on the dam came from nearby residents.

“The challenge we face now is that the valley dam contains water, but we are trying to dry it up,” Naphtal Ahishakiye, the executive secretary of genocide survivor organization Ibuka, told The Associated Press. The valley is outside the capital, Kigali, in the country’s east.

Authorities said the dam was dug years before the genocide to provide water for rice farming.

Every now and then, as graves of genocide victims are discovered, some survivors question whether true reconciliation can be realized if perpetrators of the killings conceal information about where people were buried.

Exhuming bodies during the coronavirus pandemic is very challenging since people cannot gather, Ahishakiye said. “But we try our best so that we give the dead a decent burial.”