United States President, Barack Obama has once again snubbed Nigeria as he visits select African nations on his second trip to the black continent since his election as President of the United States of America.

President Obama and First Lady Michelle Obama will visit Senegal, South Africa and Tanzania from June 26 – July 3, a statement from the White House said Monday.

President Obama’s boycott of Nigeria on his African tour is a big slap on the government of President Goodluck Jonathan, which has come under severe criticism from the US over its violation of human rights as security forces combat the terrorist group, Boko Haram.

The White House was, however, silent on why the US President snubbed Africa’s most populous state with one of the fastest growing economies in the world.

Part of the White House statement reads: “President Obama and the First Lady look forward to traveling to Senegal, South Africa, and Tanzania from June 26 – July 3. The President will reinforce the importance that the United States places on our deep and growing ties with countries in sub-Saharan Africa, including through expanding economic growth, investment, and trade; strengthening democratic institutions; and investing in the next generation of African leaders.

“The President will meet with a wide array of leaders from government, business, and civil society, including youth, to discuss our strategic partnerships on bilateral and global issues. The trip will underscore the President’s commitment to broadening and deepening cooperation between the United States and the people of sub-Saharan Africa to advance regional and global peace and prosperity,” it added.

Meanwhile, emergency crews searched the broken remnants of an Oklahoma City suburb yesterday for survivors of a massive tornado that flattened homes and demolished an elementary school.

Authorities lowered the death toll to 24, down from 51, but warned those numbers were expected to climb back up.

Some victims are believed to have been counted twice in the early chaos of the storm, said Amy Elliot, a spokeswoman for the state medical examiner’s office. Downed communication lines and problems sharing information with officers exacerbated the problem, she said.

The death toll included at least nine children. Governor Mary Fallin said authorities did not know how many people were still missing, but they vowed to account for every resident.

The ferocious storm, clocking winds of up to 200 mph (320 kph), ripped through the town of Moore in a central U.S. region known as Tornado Alley, reducing homes to piles of splintered wood. Less than 1 per cent of all tornadoes reach such wind speed.

In Washington, President Barack Obama pledged urgent government help.

“In an instant, neighbourhoods were destroyed, dozens of people lost their lives, many more were injured,” Obama said. “Among the victims were young children trying to take shelter in the safest place they knew — their school.”

The storm left scores of blocks barren and dark in Moore, a community of 41,000 people 10 miles (16 kilometres) south of Oklahoma City.

New search-and-rescue teams moved at dawn yesterday, taking over from the 200 or so emergency responders who worked all night. A helicopter shined a spotlight from above to aid in the search.

Fire Chief Gary Bird said fresh teams would search the whole community at least two more times to ensure that no survivors — or any of the dead — were overlooked. Crews painted an ‘X’ on each structure to note it had been checked.

More than 200 people had been treated at area hospitals.

Other search-and-rescue teams focused their efforts at Plaza Towers Elementary, where the storm ripped off the roof, knocked down walls and turned the playground into a mass of twisted plastic and metal as students and teachers huddled in hallways and bathrooms.

Seven of the nine dead children were killed at the school, but several students were pulled alive from under a collapsed wall and other heaps of mangled debris. Rescue workers passed the survivors down a human chain of parents and neighbourhood volunteers. Parents carried children in their arms to a triage centre in the parking lot. Some students looked dazed, others terrified.

Officials were still trying to account for a handful of children not found at the school who may have gone home early with their parents, Bird said Tuesday.

After hearing that the tornado was headed toward another school called Briarwood Elementary, David Wheeler left work and drove 100 mph (160 kph) through blinding rain and gusting wind to find his 8-year-old son, Gabriel. When he got there, “it was like the earth was wiped clean, like the grass was just sheared off,” Wheeler said.

Eventually, he found Gabriel, sitting with the teacher who had protected him. His back was cut and bruised and gravel was embedded in his head — but he was alive.

As the tornado approached, students at Briarwood were initially sent to the halls, but a third-grade teacher — whom Wheeler identified as Julie Simon — thought it didn’t look safe and so ushered the children into a closet, he said.

The teacher shielded Gabriel with her arms and held him down as the tornado collapsed the roof and starting lifting students upward with a pull so strong that it sucked the glasses off their faces, Wheeler said.

“She saved their lives by putting them in a closet and holding their heads down,” Wheeler said.

Authorities were still trying to determine the full scope of the damage.

Roofs were torn off houses, exposing metal rods left twisted like pretzels. Cars sat in heaps, crumpled and sprayed with caked-on mud. Insulation and siding was smashed up against the sides of any walls that remained standing. Yards were littered with pieces of wood, nails and pieces of electric poles.

The National Weather Service issued an initial finding that the tornado was an EF-4 on the enhanced Fujita scale, the second most powerful type of twister. It estimated that the twister was at least half a mile (nearly a kilometre) wide.

The Storm Prediction Center in Norman, Oklahoma, forecast more stormy weather Tuesday, predicting golf ball-sized hail, powerful winds and isolated, strong tornadoes in parts of Texas, Arkansas, Louisiana and Oklahoma. The area at risk does not include Moore.

Monday’s twister also came almost exactly two years after an enormous twister ripped through the city of Joplin, Missouri, killing 158 people.

That May 22, 2011, tornado was the deadliest in the United States since modern tornado record keeping began in 1950, according to the National Oceanic and Atmospheric Administration.