context: -LRB- CNN -RRB- -- Three members of a U.S. Navy helicopter crew were killed after their helicopter went down in the waters off San Diego , California , a Navy spokeswoman said Wednesday . Rescuers are still searching for the two remaining crew members from the helicopter , which went down late Tuesday night , U.S. Navy spokeswoman Karin Burzynski said . No further details concerning the deaths were immediately available . Burzynski said the helicopter was operating from the USS Nimitz . The Navy received word that the helicopter went down around 11:30 p.m. Tuesday , she said . It crashed about 20 miles off the Mexican coast , the Navy said . Coast Guard spokesman Henry Dunphy told CNN earlier that Coast Guard helicopters and boats , as well as vessels from other agencies , were helping in the search .
question: Who is using helicopters ?
answers.text: U.S. Navy
content_segment_normalized_text: three members of a u.s. navy helicopter crew were killed after their helicopter went down in the waters off san diego , california , a navy spokeswoman said wednesday .
question_normalized_text: who is using helicopters ?