There is growing alarm among Kenyan farmers about a government announcement that 2.3m bags of maize were unfit for human consumption.
Health experts say the maize contained high levels of lethal aflatoxins, which have killed at least one child.
The government has pledged to buy and destroy the contaminated maize.
The crop was harvested in the drought- and famine-prone Eastern Province and went bad because farmers lacked the appropriate storage facilities.
The east of Kenya is regularly hit by drought and food shortages.
But the BBC's Anne Waithera in Makindu, eastern Kenya, said heavy rains last year prompted a bumper harvest.
Farmers were not expecting so much maize and did not know how to store it properly, our correspondent says.
Maize can be hit by a toxic fungus if it is not stored properly.
There have reportedly been more cases of maize-related food poisoning, and farmers in areas where the maize was harvested have told the BBC they are still not sure what is safe to eat.
One farmer told the BBC the government was offering to buy the maize for much less than it was worth.
He also said he was trying to select only the good maize to feed his family, but did not know for sure which bags were contaminated.