"There were around 150 people on board. 50 have been rescued. We have alerted districts downstream to watch out for bodies," an Adamawa State official William Zai Wali told French news agency AFP.

The boat was carrying passengers, cement and fuel down the Benue river from Numan in Adamawa State to Jen in Taraba State when it hit a bridge and turned over.

"The river was full because water was being released from the dam at Loddu," he said. "The ferry hit the piles of a bridge across the river and capsized."

But a Nigerian Red Cross spokeswoman said she had not yet heard of any survivors.

"There is no news of any rescued alive yet," said Umo Okon. She added that Red Cross rescue workers were still searching for survivors. She was unable to say whether rescue teams at the scene had recovered any bodies.

Numan is 700km (440 miles) east of the Nigerian capital Abuja.

Nigeria's waterways and roads are the scenes of frequent accidents, due to the bad state of passenger boats, vehicles and roads.