Flash flooding across Nigeria’s southwest killed at least 102 people in the last week, the country’s Red Cross said Wednesday.

Some 1,500 people remain displaced by the torrential downpours, officials said.

The major flood hit hardest in Oyo state’s capital of Ibadan. Heavy rains there on Friday made a local dam overflow, sending water crashing through the informal settlements surrounding the city.

The water also damaged three bridges in the area, trapping people in their neighbourhoods, said Tunde Adebiyi, an official with Nigeria’s National Emergency Management Agency.

Many homes were poorly constructed, meaning they simply washed away when the water rushed through, said Umar Mairiga, an official with the Nigerian Red Cross.

”I think in the process a lot of them were washed away by the rainwater and others were trapped in collapsed buildings,” Mairiga said Wednesday.

Mairiga said it took time to get a proper casualty figure as water levels in some areas remain high as seasonal rains continue throughout Africa’s most populous nation.

Nigeria’s emergency agency had warned that rains will be heavier this year than last year. In an assessment after the flooding, the agency said more flooding would be likely in areas with inadequate drainage and improperly disposed trash, a common problem in Nigerian neighbourhoods where zoning laws are rarely heeded or enforced.

Last year, some 500,000 people were displaced nationwide by floods in Nigeria.

Nigeria’s rainy season lasts roughly from June to September. The rains paused for most of August this year, however, only starting again within the last week.