The Shakahola forest "where grave crimes have been committed will not remain as it was," Interior Minister Kithure Kindiki said on Tuesday.
"The government will convert it into a national memorial, a place of remembrance so that Kenyans and the world do not forget what happened here," he said in a statement.
The discovery of mass graves in Shakahola forest, a 325-hectare bushland that lies inland from the Indian Ocean town of Malindi, has shocked Kenyans.
Cult leader Paul Nthenge Mackenzie is facing various charges in the grisly case, accused of driving his followers to death by preaching that starvation was the only path to God.
Investigators began a third phase of exhumation on Tuesday, unearthing nine more bodies to take the death toll to 251.
Kindiki said the cult's activities extended beyond Shakahola forest and that "comprehensive, methodical, and scientific" investigations had extended to a ranch in the area stretching over more than 14,980 hectares.
Investigators began a third phase of exhumation on Tuesday, unearthing nine more bodies to take the death toll to 251.
While starvation appears to be the main cause of death, some of the victims - including children - were strangled, beaten or suffocated, according to autopsies carried by the government.
"Once the ongoing exercise is concluded, a congregation of believers from all faiths and the national leadership shall convene for a commemoration service," Kindiki said.
Mackenzie - a taxi driver-turned-preacher - has not yet been required to enter a plea, with the prosecution seeking for more days to detain him pending further investigations.
The 50-year-old founder of the Good News International Church turned himself in on April 14 after police acting on a tip-off first entered Shakahola forest.
Police say at least 35 people have been arrested.
Some 95 people have been rescued from the forest while the number of those reported missing was 613, according to police records.
Questions have been raised about how Mackenzie, a father of seven, managed to evade law enforcement despite a history of extremism and previous legal cases.
The horrific saga led President William Ruto to set up a commission of inquiry into the deaths and a task force to review regulations governing religious bodies.
Efforts to regulate religion in the majority-Christian country have been fiercely opposed in the past as attempts to undermine constitutional guarantees for the division of church and state.
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