A torrential downpour and strong winds prevented emergency crews from returning on Tuesday morning to a devastated neighbourhood where a commercial airliner crashed, killing all 153 people aboard the plane and an undetermined number of people on the ground.

The storm began on Tuesday morning before dawn, flooding roads and bringing down power lines and trees in Lagos, Nigeria’s largest city. Traffic crawled through the area, stopping searchers from returning to the site, said Yushau Shuaib, a spokesman for Nigeria’s National Emergency Management Agency.

Charred metal from the plane, rubble from destroyed buildings, thick mud and standing water await the emergency workers. A three-storey apartment building at the site struck by the nose of the MD-83 aircraft began shaking on Monday as rescuers dug through debris, and they are afraid it might collapse.

“It’s going to be messy,” Shuaib said.

The crash happened on Sunday afternoon in Lagos’ Iju-Ishaga neighbourhood, about nine kilometres (five miles) from Lagos’ Murtala Muhammed International Airport. Pilots on the flight from Nigeria’s capital Abuja to its largest city of Lagos radioed the tower that they had engine trouble shortly before the crash, but the exact cause remained unclear. The weather was clear at the time.

Late on Monday, emergency workers recovered both the flight data recorder and the cockpit voice recorder, said Tunji Oketunbi, a spokesman for the Accident Investigation Bureau, which probes airplane crashes in Nigeria.

“We will take them abroad for decoding and that will help our analysis,” Oketunbi said on Tuesday. “We will know what happened to the aircraft shortly before it crashed.”

An investigator from the U.S. National Transportation Safety Board also is expected to join Nigerian authorities on Tuesday to help them determine a cause for the crash, Oketunbi said.

By nightfall on Monday, searchers with police dogs recovered 137 bodies, including those of a mother cradling an infant, according to Nigeria’s National Emergency Management Agency. Rescuers acknowledged they don’t know how many people died in the wrecked apartments and smaller tin-roofed buildings along the narrow streets of Iju-Ishaga.

President Goodluck Jonathan wept as he visited the crash site on Monday and pledged to make air travel safer, but the crash called into question the government’s ability to protect its citizens and enforce regulations in a nation with a history of aviation disasters.

Some U.S. citizens were aboard the flight, State Department spokesman Mark Toner said, but he could not provide a firm number. A woman from West Hartford, Connecticut, her husband and four young children died on board the flight. The Tuesday edition of the Hartford Courant newspaper identified the family as Maimuna Anyene, her Nigerian husband Onyeke, and their children, a 5 month old, 1-year-old twins and a 3 year old.

The Houston Chronicle reported on Tuesday that the crash also killed Josephine and Jennifer Onita, sisters from Missouri City, Texas.

Others killed in the crash included at least four Chinese citizens, two Lebanese nationals and one French citizen, officials said.

Boeing said in a statement on its website that the company is ready to provide technical assistance to the Nigerian Civil Aviation Authority through the U.S. National Transportation Safety Board. Dana Air said an investigation was under way with U.S. officials assisting the Nigerian government.

Nigeria, home to more than 160 million people, hasn’t had a major airline crash in recent years. On Saturday night, a Nigerian Boeing 727 cargo airliner crashed in Accra, the capital of Ghana, slamming into a bus and killing 10 people. That plane belonged to Lagos-based Allied Air Cargo.

Sunday’s crash was the deadliest in nearly two decades. In September 1992, a military transport plane that crashed after taking off from Lagos killed 163 people.

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