The staff at the crematorium noticed the bodies and informed the Bharalumukh police station, he said.
It is not clear how the bodies surfaced on the river but police suspect that they were buried by the Gauhati Medical College Hospital staff in the sand bars next to the river, the officer said.
As the water level rose in the river following rain over the past few days, the sand bars may have broken, causing them to float on the river, he explained.
The seven bodies will have to be kept in the morgue for the next 72 hours and then disposed of as per orders from the civil magistrate, the officer said, adding that the remains will be buried near the crematorium.
The river police has been being pressed into service to recover the seven bodies.
The authorities at the Bhootnath Crematorium said the GMCH employees often buried unidentified bodies on the river bank without informing them.