SYDNEY, Australia — Officials expressed new optimism on Thursday that data from an attempt to contact the Malaysia Airlines flight that disappeared in the Indian Ocean could lead to the plane’s discovery.

“All of the countries involved remain cautiously optimistic that we will find the missing aircraft,” Australia’s deputy prime minister, Warren Truss, said at a news conference in Canberra, Australia’s capital, with the Malaysian transportation minister, Liow Tiong Lai, and China’s vice minister for transport, He Jianzhong.

Mr. Truss said teams continued to refine the search area almost six months after the plane, Flight 370, vanished, noting that data from a failed attempt to contact the plane with a satellite phone had provided some new information.

“After MH370 disappeared from the radar, Malaysia Airlines ground staff sought to make contact with the aircraft using a satellite phone,” Mr. Truss said. “That was unsuccessful. But the detailed research that is being done now has been able to identify or trace that phone call and help to position the aircraft and the direction it was traveling. That has suggested to us that the aircraft may have turned south a little earlier than we had previously expected.”