State officials were investigating complaints of negligence by hospital authorities in the state capital Chennai, which is reeling from unprecedented floods.
The 18 patients were in the intensive care unit when a power outage affected ventilators in the hospital, leading to their deaths over the past two to three days, said Health Secretary J. Radhakrishnan.
He said that flood waters entered the room with the generators, cutting off power to the building and switching off the ventilators.
Army soldiers using boats have rescued thousands of residents marooned in high-rise buildings and launched massive relief operations to provide food and medicines.
Although flood waters have begun to recede, vast swathes of Chennai and neighboring districts were still under 8-to-10 feet (2 ½-3 meters) of water, with tens of thousands of people in state-run relief camps.
As officials struggled to supply drinking water and food packets, people were complaining that relief had not yet reached several neighborhoods, four days after they were marooned or stranded on rooftops. Chennai's airport was closed for a fourth day Saturday, although some flights operated from a nearby air force base.
India's main monsoon season runs from June through September, but for Chennai and the rest of India's southeastern coast, the heaviest rainfall is from October to December — also called the retreating monsoon.
This year's deluge — which experts linked to the El Nino weather pattern, when the waters of the Pacific Ocean get warmer than usual — caught Chennai, with a population of 9.6 million, completely unprepared.
(AP)
Flood affected people receive food packets being distributed by navy personnel in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
Patients wait to be shifted out after the hospital they were being treated in had to be shut down because of power failure and being inundated with floodwaters in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
In this photo provided by the Press Trust of India, a woman who lost a relative in the floods cries as she speaks on the phone at a hospital in Chennai, India, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
Flood-affected people stretch out their hands to receive packets of biscuits being distributed in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
A Coastguard chopper airlifts a sailor after he delivered food material to a residential area flooded due to heavy rainfall in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
A woman cries after seeing the corpse of her son floating in the Adyar River after he was washed away by floodwaters in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 4, 2015. The relentless rains that lashed the state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.
National Disaster Response Force personnel carry an elderly sick man from a residential area flooded due to heavy rainfall in Chennai, in the southern Indian state of Tamil Nadu, Friday, Dec. 04, 2015. The relentless rains that lashed southern India's Tamil Nadu state for three days eased Friday, but the misery of tens of thousands of people was far from over, with large parts of the main city still underwater along with the region's biggest airport.