Mr Njoroge's brother William, 30, an auditor, worked in the now demolished Ufundi House, next door to the US embassy, where frantic rescue efforts to reach survivors, entombed by rubble, continued last night.
Outside in the mortuary gardens, relatives passed through bright orange flowers springing from neat, well tended beds. Inside the bare white rooms, where blood congealed on stone floors, one man lay naked on a slab, intestines erupting from his open stomach. It seems impossible that some believe that "heroism" like this leads straight to heaven.
"Just pray for our brother," said Mr Njoroge, emerging to tell 20 waiting relatives that William was not inside. For two days they have been bounced from hospitals to morgues to view the dead, listened to lists of victims called out by megaphone and run their eyes down rows of names pinned to mortuary gates. It has been a strangely silent, undemonstrative business.
The huge Njoroge clan was marooned between desire to know the worst and the need to cling to hope. "You have seen the building," says Mr Njoroge. "Is there still hope? We still think William might be alive under the rubble.''
At Ufundi House the rescue teams, led by a 200-strong Israeli team that arrived on Saturday afternoon, were working to make almost-impossible dreams come true. But time is running out. The International Committee of the Red Cross estimated that 10 people might still be trapped, among them girls from a secretarial college housed in the building.
It has been a weekend of back- and heart-breaking work. Mostly, rescuers have only retrieved the crushed and deformed bodies of the dead. Only one man has been pulled alive from the rubble though rescuers have come tantalisingly close to saving others.
On Saturday night David Kambi, a Kenyan engineer, fought for four hours to reach a 40-year-old man pinned down by concrete. He talked to the trapped man to keep his spirits up but he died seconds before the team reached him. He used his final breath to thank the rescuers and to apologise for failing to hold on.
The rescue operation is extremely dangerous, with the building constantly on the move. Its precarious condition halted early attempts to burrow underneath the rubble. Now the rescuers are clearing from the top. After an initial, pitiful lack of resources, heavy slabs of concrete are now being removed by a 150-tonne crane, drills and blow torches. But the most delicate work continues to be performed by hand.
Rescuers were visited yesterday by Kenyan President Daniel Arap Moi who said the bombers had simply alienated Kenyans. "How can they expect Kenya to support their cause if they use such methods?" he said. "Even if they wanted the US embassy they should not have targeted Kenyans. Kenyans are peaceful people.''
It is hard not to make third world-first world comparisons. The US embassy in Nairobi, the target of Friday's bomb attack, stands largely intact, its bomb-proof windows loose but unbroken. Just behind the American building is a hole where Ufundi House once stood. With no hi-tech building materials to protect it, its four floors were reduced to rubble and twisted, tangled metal.
Kenyans complain that the US has not helped in the recovery of hundreds of office workers and secretarial students from the Ufundi block. The US, they say, has selfishly and insensitively concentrated on its own nationals - 11 Americans are confirmed dead. Their complaints are privately echoed by journalists and aid workers.
"They should have helped us," said one man, searching for a missing relative. "After all we are innocent. We have nothing to do with American and Arab problems." While he blamed the bombers for mass murder, he said the US should have moved its embassy from the city centre and criticised it for failing to maintain security standards, particularly with hostile Sudan as a close neighbour.
Nina Galbe, regional spokeswoman of the International Committee of the Red Cross, tried to be diplomatic. "While we understand that the Americans were concerned foremost with their own nationals and general security in their building, a greater US presence would have been welcomed, given the extent of suffering in Kenyan society.'' She said the effect on Kenya would be profound and long-lasting. Many Kenyans who perished in the explosion were sole bread winners for huge extended families.
Until the arrival of the Israeli experts, rescue efforts - led by Kenyans, digging with their bare hands, and local Asian businessmen, operating their own construction equipment - was well-meaning but pitifully amateur. Ms Galbe says people died because of the lack of swift co-ordinated action.
More than 20 FBI agents arrived in Nairobi last night to join two colleagues who arrived on Friday. There are plenty of theories circulating. The Nairobi Sunday Nation newspaper yesterday carried an interview with a security man who claims to have seen three Arabs secretly filming the embassy just four days before the blast. But US security guards, he says, dismissed him, saying the three were probably tourists.
Other witnesses have described what appears to have been a suicide bomber. They say they saw a man drive into the embassy's rear parking bay and sit inside his car until the explosion.
FBI spokesman Frank Scafidi said yesterday that the priority was to determine what explosive was used and how it was transported to the scene. That information he said "can be like a fingerprint of who did it." The American Embassy in Tanzania, where the second terrorist bomb exploded on Friday, last night said it might have a video of the bombers.