Malaysian official raises the possibility of more underwater search vehicles . The Australian Transport Safety Bureau (ATSB) said it was investigating whether a new type of submersible vehicle could be used to help locate MH370. Bluefin-21 has covered 110 square kilometers in four trips . Officials did n't indicate whether Bluefin 's fourth mission was a lengthy one . A preliminary analysis of an oil sample shows that it is not aircraft engine oil .
Malaysian official raises the possibility of more underwater search vehicles . The Australian Transport Safety Bureau (ATSB) said it was investigating whether a new type of submersible vehicle could be used to help locate MH370. Bluefin-21 has covered 110 square kilometers in four trips . A preliminary analysis of an oil sample shows that it is not aircraft engine oil .