A court in Naivasha town has acquitted nine people charged with causing the deaths of nearly 50 people in the Patel dam tragedy two years ago, after strongly criticising the prosecution.
The nine - including dam owner Perry Mansukh - were facing manslaughter charges.
But after 18 months in court, Naivasha Chief Magistrate Kennedy Bilali set the suspects free, citing the slow progress of the case.
He accused the prosecution of holding the court hostage with endless adjournment requests, saying the accused deserved a fair trial.
State counsel Catherine Mwaniki said she would appeal against the ruling.
The Patel dam - on a sprawling farm near Solai, 190km (120 miles) from the capital, Nairobi - burst its banks in May 2018 following a period of heavy rains.
The huge water mass swept through the Solai plantation settlement, killing dozens and destroying property.
State-sanctioned and independent investigations blamed the dam owners for flouting environmental regulations and substandard construction for the collapse.
They always denied any wrongdoing.