The investigation into Saturday's plane crash in the Bahamas that killed singer Aaliyah, 22, and eight others widened on Monday as U.S. officials joined efforts to determine what caused the aircraft to go down shortly after takeoff. The U.S. National Transportation Safety Board sent a four-person team of safety experts to Marsh Harbor -- one from the NTSB, one from the U.S. Federal Aviation Administration, one from Cessna and one from Continental Motors, which manufactured the plane's engines -- a U.S. Embassy spokesman told Reuters. Investigators will reportedly probe suggestions that the plane might have been overloaded. The Cessna Aircraft Co. said the Cessna 402B plane could carry up to 1,340 pounds of baggage, but there was no indication how much was aboard. One witness, pilot Claude Sawyer, 25, told the Associated Press that he was alongside the runway when the plane started to plummet. "It appeared to be a normal takeoff," said Sawyer. "It departed, and (the pilot) rotated the nose (of the plane) and lifted off the ground. After that he pulled his landing gear up and then the plane veered slightly to the left and then it went toward the ground." Sawyer said he watched the plane disappear below the trees and then saw a ball of fire. He could not hear any engine noise. The music star had gone to the destination to shoot a music video with noted director Hype Williams and had spent all day Friday and Saturday, beginning at 4:30 a.m., filming with no time off, other than for eating and sleeping, says the New York Post. Aaliyah's boyfriend, Roc-A-Fella Records CEO Damon Dash, is in seclusion but issued a statement saying, "I am crushed and heartbroken over the loss of such a beautiful woman whom I loved deeply and who meant the world to me." Meanwhile, on Monday, Aaliyah's music played in the background as hundreds gathered near her former high school, Detroit's High School of Fine and Performing Arts, for a candlelight vigil in the singer's honor. People carried posters and signs attesting to their love of Aaliyah.