A private jet en route to Houston to pick up President George W. Bush's father was hundreds of feet lower than it should have been when it hit a light pole and crashed, but federal investigators say it's too early to say what caused the wreck that killed three crew members. The Gulfstream G-1159A plane went down early Monday about 3 1/4 miles south of a runway at Hobby Airport, officials said. The area was covered in thick fog at the time. Mark Rosenker, vice chairman of the National Transportation Safety Board, said the light pole clipped by the plane was 36 meters (120 feet) high and the normal altitude for the jet at that point from the runway would have been 300 meters (1,000 feet). The jet was to pick up former President George H.W. Bush, who lives in Houston, for a trip to Ecuador to give a speech at a business conference, his spokesman Tom Frechette said. Rosenker said the agency's 15-person investigation team would examine "a number of factors," including the condition of the aircraft, the weather and the history of the flight crew. He said standard toxicology tests would be performed on the bodies of the two male pilots and one female flight attendant who died in the crash. Their names were not released Monday. "I was deeply saddened to learn of the plane crash this morning," Bush said through Frechette. "I'd flown with this group before and know them well. I join in sending heartfelt condolences to each and every member of their families."