Flooding hampers clean-up efforts in Oklahoma Tornadoes that ripped through Oklahoma killed nine people, including two children, officials said, as flooding hampered cleanup efforts in the US state recently ravaged by a monster twister. The Medical Examiner's Office revised the death toll upward from five in the wake of Friday night's storms that battered areas in and around Oklahoma City with high winds and heavy rain. Five of the victims have not been identified. The Oklahoma Department of Emergency Management said earlier that a mother and child perished as they travelled in their car on an interstate highway. It was not immediately clear how many people were injured by the series of storms that struck the area around Oklahoma City. Local broadcaster KOCO said on its website that 77 people had been admitted to hospitals with storm-related injuries. Reports said five twisters had struck with winds of up to 90 miles (145 kilometres) per hour, accompanied by very large hail. Flash floods also hit the area, the Tulsa World newspaper said. The National Weather Service's Storm Prediction Center in Norman, Oklahoma, said the first tornado developed around the city of El Reno before moving into parts of Oklahoma City, spawning others. Saturday also marked the official start of a US hurricane season in which some forecasters have said there could be more extreme weather coming in from the Atlantic, triggered by warmer than average water temperatures. As the extent of the devastation in Oklahoma became clear, the work of cleanup crews was complicated by downpours that drenched the region overnight. Officials from hard hit Canadian County, speaking on CNN, said crews were working to assess and restore ""washed out"" places. A trailer park in Oklahoma City was among areas evacuated Saturday morning by boat, raft and Humvee, according to KOCO. Photos showed streets looking like rivers, with stranded cars submerged in water as high as their door handles in some places. Officials for Oklahoma City's Will Rogers World Airport said on Twitter that passengers had been evacuated to an underground tunnel and that flights in and out had been suspended. Friday's storms were far less damaging than the tornado that hit the Oklahoma City suburb of Moore nearly two weeks ago that left 24 dead and demolished large swathes of the town.