While nine mentally ill patients have returned to the Mathari Mental Hospital in Kenya after being recovered by their guardians and parents, 31 patients are still on the loose, spurring a frantic police search that began on Sunday, police told BBC.

The Mathari Mental Hospital is a state hospital based in Nairobi, the country's capital, and is also the biggest psychiatric hospital in the country. Kenyan newspapers reported that a group of patients were complaining about the poor medication they were receiving.

Police chief Samuel Anampiu told the Associated Press that nearly 70 patients, all male, overpowered the hospital guards and let 40 escape early on Sunday.

Moses Ombati, a senior Nairobi police officer, told BBC that they also began a protest before overriding the guards.

Anampiu announced the patients' escape to Kenya's newspapers and said the police are using the patients' belongings and pictures to help with the identification process.

The hospital's medical superintendent, Kisivulu Azenga, said the patients are not harmful to society, but need to be reported and returned to resume treatment.

The last escape attempt involved only two to three patients.