The stampede broke out after a staircase leading to a river jetty caved in early morning while the pilgrims were about to board a vessel to reach the Gangasagar islands, the police said.
Five pilgrims died on the spot, while two others including a 4-year-old child were declared dead when brought to a temporary hospital at the island.
The condition of four of the injured was reported to be serious. They have been shifted to Diamond Harbour hospital in South 24 Parganas district.
The dead who were identified had come from Uttar Pradesh and Haryana. Around four lakh pilgrims had gathered to take a holy dip at the confluence of Ganga and the Bay of Bengal in the islands.
“We have asked the district administration to investigate the matter and find out the actual reason behind the mishap. We will also look into the aspect if anybody was responsible for the tragedy,” state chief secretary Ashok Mohan Chakraborty told reporters here.
According to South 24 Parganas district magistrate Khalil Ahmed who put the number of those injured at nine, several pilgrims tried to board a boat in a hurry at jetty number three as the 12-hour bundh by the CPM in the district delayed their arrival. This could have triggered the stampede. The pilgrims had been warned not to board any vessel because of the low tide, but they declined to heed the caution, he added.