(AFP) - Rescue operations were under way on Monday to find survivors of a capsized boat in northwestern Nigeria, authorities said, after at least five people drowned and a dozen went missing.

Up to 40 people were initially feared to have drowned in the accident, including women and children, which occurred when the vessel was crossing a river in Jigawa state, police said.

But as of Monday afternoon, 23 of the estimated 40 passengers had been found alive, they said.

Around 12 are still unaccounted for.

Such accidents are common on Nigeria`s busy rivers and waterways, often caused by overloaded boats, poor maintenance or failure to comply with safety regulations.

Scores die each year.

Police spokesman Shi`isu Adam told AFP a body was recovered on Sunday and five more were found early on Monday.

The National Emergency Management Agency (NEMA) gave a lower toll, saying that only five people were confirmed dead.

"The search and rescue is still ongoing," Nura Abdullahi, Jigawa state spokesman for NEMA, told AFP.

Rains are currently inundating the west African country, which is in its annual rainy season.

But Abdullahi said they were not a factor in Sunday`s accident.