Low-lying Bangladesh, with extensive inland waterways and slack safety standards, suffers regular ferry disasters, with deaths sometimes running into the hundreds.
In Sunday's incident, rescuers pulled the body of a baby from the water and are searching for additional survivors.
"The ferry capsized as it was hit by a cargo vessel,"  regional police official Bidhan Tripura said, adding that police had seized the trawler and arrested two of its crew.
A police team, assisted by firemen and the Bangladesh Inland Water Transport Authority, is trying to salvage the ferry, he said.
The ferry was heading to Paturia from Daulatdia in Rajbari, located on the opposite bank of the river and 136 km (85 miles)northwest of Dhaka, the capital.
A similar accident on February 13 killed at least seven passengers in southern Bangladesh.

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