A tourist boat packed with tourists capsized in southern Kerala, India. At least 22 people died.

As rescue efforts begin on Monday, and as the vessel is pulled out of muddy water, the death toll may rise.

Overcrowding caused the double-decker boat to capsize, Abdul Nazar, junior superintendent of police of Malappuram district, told Reuters.

The boat was reportedly carrying about 50 people, or double its capacity, when it overturned on Sunday night.

On Twitter, Indian Prime Minister Narendra Modi offered his condolences. He said he was "pained by the loss of lives".

Local media reported that many passengers were trapped underneath the boat, and the darkness hampered rescue efforts. Women and children who were on holiday were among the victims.

V Abdurahiman, Kerala's Sports and Fisheries Minister, stated that at least four of the people taken to the hospital were in critical condition.

The exact number of missing passengers was not immediately clear. Authorities said they are investigating the cause of the mishap.

Shameer, a lifeguard involved in the rescue operation, told Mathrubhumi news channel that "the boat was completely upside down" when rescuers arrived at the scene. "I recovered four bodies and none of them had life jackets on."

Many of the other passengers were also not wearing life jackets at the time of the incident, survivors told local media.

Ambika, a resident of the nearby Tanur area, told Manorama news channel that when she first saw the boat approach, everyone seemed to be "cheering happily".

"But suddenly the lights went out, the boat sank and the cheers were replaced with screams for help," she said.

Ms. Ambika added that she immediately called the police for help. "But we could not do anything beyond that because it was getting dark and there was no way to reach the passengers."