At least eight merrymakers were swept away while bathing in Sultangarh Waterfall in Shivpuri district of Madhya Pradesh on Wednesday, police said.
Over 40 others are stranded as of tonight, they said.
"Eight persons have been swept away in the waterfall following a sudden surge in the water," Shivpuri district Superintendent of Police (SP) Rajesh Hingankar told PTI.
No bodies have been found yet and it could not be ascertained whether the missing persons have drowned, another police official said.
"Nearly 45 others are still stranded near the waterfall and we are unable to carry out rescue operations by helicopter now due to darkness," the SP said.
Eyewitnesses had earlier claimed that more than ten persons who were bathing in the waterfall were swept away.
A team of National Disaster Response Force (NDRF) is involved in the rescue along with the state police.
The helicopter, in its first sortie, rescued five persons who were stranded on a rock in the water downstream, while two more were saved by local people, the SP said.
The waterfall is near Mohana village, 55 km from the district headquarters, in an area bordering Gwalior district.
Tourists had thronged the place on Wednesday due to the Independence Day holiday.
There was a sudden surge in water around 4.30 pm, possibly due to heavy rain upstream, catching those bathing in the waterfall unawares, police said quoting the locals.