HANGZHOU -- Seven officials have been held accountable for the contamination of running water in Yuhang district of Hangzhou, the capital of East China's Zhejiang province, the municipal government said on Wednesday.

The seven officials include a deputy district head, as well as officials of the district's housing and urban development bureau, according to a report issued by a joint investigation panel organized by the municipal government.

The investigation found that substances detected in water samples were organic sulfur compounds that can emit odors similar to garlic, swamps or decay, even in low concentrations.

Since early July, sustained high temperatures have triggered rapid algae blooms in the upstream of Dongtiao River, and in bodies of water near the intake area of the Renhe water plant. Rainfall over a period of days led to concentrated runoff, resulting in the accumulation of algae and related degradation products -- including substances with a sulfurous odor -- near the intake area, and that runoff was processed by the plant early on July 16.

A comprehensive analysis concluded that the unusual odor in the water supply had resulted from a combination of climatic, environmental and hydrodynamic factors.

Members of the investigation panel include officials of the city's administrative law enforcement, ecology and environment, and health authorities, as well as national and provincial-level experts, under the guidance of provincial government departments for construction and ecology and environment.

Following the incident, authorities in the water supply sector comprehensively reviewed all 33 urban water plants across Hangzhou, and confirmed that the quality of water leaving these plants meets standard requirements.

The free replacement of water purifier filters will be available for affected families, and residents of the 49 affected communities in the area will have their water fees waived in full in July, the report said.