A wide brown scar of mud, uprooted trees and crushed houses slices through the area of Mai Mahiu, at the border of Nakuru and Kiambu counties.

A roaring sound woke people up in the early hours of Monday as a tide of water crashed down from upriver.

Residents spoke of a night of frantic efforts to pull people out of the raging flood and dig them out of the mud.

Deden Muiri, 60, said he heard the roar and saw a lightning flash. But before he had time to think he was up to his neck in water.

He saw the flood take his wife and was swept in the opposite direction.

Convinced he was going to die, Muiri said a quiet goodbye to his family.

Miraculously though, he was able to grab a tree branch and clung to life by hanging on.

One of his daughters knows how to swim, he said, and was able to rescue two of his grandchildren.

When we arrived many people were out surveying the damage, walking along the gauged-out riverbank, poking through the debris, trying to come to grips with the catastrophe.

Peter Munyinge’s house survived but the rest of his neighbourhood did not.

“There are little babies in the water, older people…people are screaming, people are crying, losing their lives and their loved ones,” he said.

The Kenya Red Cross joined search and rescue operations, with its emergency response manager, Anthony Muchiri, telling the BBC that the death toll has risen to 50.

Deden Muiri, 60, said he heard the roar and saw a lightning flash. But before he had time to think he was up to his neck in water.

He saw the flood take his wife and was swept in the opposite direction.

Convinced he was going to die, Muiri said a quiet goodbye to his family.

Miraculously though, he was able to grab a tree branch and clung to life by hanging on.

One of his daughters knows how to swim, he said, and was able to rescue two of his grandchildren.

When we arrived many people were out surveying the damage, walking along the gauged-out riverbank, poking through the debris, trying to come to grips with the catastrophe.

Peter Munyinge’s house survived but the rest of his neighbourhood did not.

“There are little babies in the water, older people…people are screaming, people are crying, losing their lives and their loved ones,” he said.

The Kenya Red Cross joined search and rescue operations, with its emergency response manager, Anthony Muchiri, telling the BBC that the death toll has risen to 50.

“This is the worst I’ve ever come across in my career,” he said, adding that not only were people’s homes swept away, but also their foundations.

Of the bodies recovered so far, 17 were of children, police commander Stephen Kirui said, cited by Reuters news agency.

The sudden wave of floodwater was initially attributed to a nearby burst dam by local officials.

However, the Kenyan Ministry of water, sanitation and irrigation said on Monday evening that the incident occurred as a result of a tunnel – which channels the River Tongi under a railway line – becoming blocked with “debris, stones, trees and soil” during the recent downpours.

This prevented water flowing through it from moving downstream, leading to a pool of water suddenly sweeping over the railway line, the ministry said in a statement.

“The area has no dam and the only dam upstream in a different tributary is the Matches Dam which is in good condition and stable,” it added.

The small villages of Kamuchiri and Kianugu were among those that bore the brunt of the disaster.

Peter Muhoho said that most of his neighbours were swept away in Kianugu, a village with about 18 homes.

“I was asleep when I heard a loud bang and screams. Water had flooded the area. We started rescuing people,” Mr Muhoho told the BBC.

Pointing to a bag he was holding, Mr Muhoho added: “This bag belongs to a chid I knew. He was washed away. I found it [the bag] downstream.”

The government has delayed the opening of schools across Kenya with more rain expected, according to forecasters.More than 130,000 people have been displaced by the floods, with many people taking shelter in schools.