At least 23 people drowned when a bus travelling to a wedding in central Kenya was swept off a bridge into a flooded river.

“We have this terrible, terrible accident that happened here this morning,” Kitui governor Charity Ngilu told reporters on Saturday.

“The bodies that have already been retrieved right now are over 23. We have more bodies in the bus,” she said, adding efforts to recover the corpses would resume on Sunday morning.

Ngilu on Twitter posted that together with the Kenya Red Cross and law enforcement agencies they were “doing everything possible to search and rescue as well as recovery”.

She said 12 people had been rescued, including four children. It remains unclear how many passengers were aboard the bus.

The choir members of Mwingi Catholic Church had been travelling for their male colleague’s wedding when the accident occurred in Kitui County.

Witnesses said the driver was trying to cross fast-flowing waters passing over the bridge but the force was too strong, sweeping the bus beneath the churning currents.

Deputy President William Ruto was among those to extend his condolences, and also urged motorists to apply extra caution on the roads with many parts of Kenya experiencing heavy rain.

Officials said the incident is under investigation.