<div>In the United States, four people were injured, one seriously, when a medical helicopter crashed on a highway in Chicago, Illinois, last night. According to the Federal Aviation Authority, the Eurocopter 135 air ambulance crashed on a ramp of the Interstate 57 highway soon after the pilot made a "Mayday" radio call. <br />''</div>''<div><br />''</div>''<div>The local media report said a patient on the air ambulance was in critical condition, while the pilot and two others on board were listed in stable condition in Chicago hospitals. No one on the ground was injured and the National Transportation Safety Board has launched an investigation into the crash. </div>''<div><br />''</div>