At least five people were killed Thursday after inhaling poisonous gas at an aqua food processing plant in southern Indian state of Andhra Pradesh, officials said.

The workers were cleaning a chemical tank at the food processing plant in Nallavari Cheruvu village of West Godavari district, about 140 km northeast of Amaravathi, the main city of Andhra Pradesh.

"Today five workers were killed inside an aqua food processing factory here after inhaling poisonous gas. Three people died on the spot, while as the other two succumbed in the hospital," a police official posted in West Godavari told Xinhua.

"The incident occurred when the workers entered into a tank in the plant to clean it," he added.

According to officials, the aqua food plant is a prawn processing and export unit.

Police registered a case and ordered a probe into the mishap.

Labour union leaders in India often accuse factories and mills of ignoring safety standards.

Source: Xinhua