Twenty-six patients at Cuba's top hospital for the mentally ill died this week during a cold snap, the government said Friday.

Human rights leaders cited negligence and a lack of resources as factors in the deaths, and the Health Ministry launched an investigation that it said could lead to criminal proceedings.

A Health Ministry communique read on state television blamed "prolonged low temperatures that fell to 38 degrees Fahrenheit in Boyeros," the neighborhood where Havana's Psychiatric Hospital is located.

It said most of the deaths were from natural causes like old age, respiratory infections and complications from chronic diseases including cancer and cardiovascular problems.

But the statement corroborated reports from the independent Cuban Commission on Human Rights that least 24 mental patients died of hypothermia, and that the hospital did not do enough to protect them from the cold because of problems such as faulty windows.

Commission head Elizardo Sanchez said that so many patients dying of hypothermia was "absurd in a tropical country" and claimed the deaths could have been prevented if the government had granted long-standing requests from international aid groups to tour Cuba's medical facilities, including the capital's 2,500-bed mental hospital.

The Health Ministry said a commission created to investigate has already identified various deficiencies.

Communist Cuba provides free health care to all its citizens but, though the quality of its medical system is celebrated in leftist circles around Latin America, it is also plagued by shortages. Patients are expected to bring their own sheets and towels and sometimes their own food during hospital stays.

Cuba blames the shortages on the U.S. trade embargo, though it does not prevent the direct sale of medicine or medical supplies to the island.