Police in India are investigating the organizers of a Hindu religious gathering in the country's north. At least 121 people were killed there in the country's worst stampede in years.

The stampede happened on Tuesday in the state of Uttar Pradesh, some 200 kilometers from the capital, New Delhi.

Local officials say tens of thousands of people had gathered at an outdoor venue in the sweltering heat to hear a speech by a spiritual leader.

One survivor said: "The stampede occurred after the preaching ended. Anyone who fell did not get up, was trampled by the crowd and died."

Most of the people who died were women. Police say more than 30 people are being treated at hospitals.

Police have registered a case against the organizers of the event for culpable homicide not amounting to murder. Investigators believe the organizers allowed people to gather beyond the permitted levels.

Stampedes and other accidents at religious gatherings have repeatedly occurred in India. They are often blamed on poor crowd management. In 2013, more than 100 pilgrims died in a crowd crush on a bridge while heading to a temple in the central state of Madhya Pradesh.