For the first time since the search began a month ago, the tone of investigators briefing media on the search for missing Malaysia Airlines Flight 370 has changed. “We are encouraged that we are very close to where we need to be,” Australian chief of search operations Angus Houston told the press today.

After a major breakthrough late last week that investigators had received signals at 37.5kHz, the frequency at which airplane black boxes and flight records are set to ping, investigators are increasingly confident they are near the location of the aircraft. After Chinese vessel Haixun 01 first heard several minutes of such a frequency, Australian and American aircraft found similar energy waves in the same area. 

While Houston refused to say “this is it” definitively, he described this new lead as “the best information we have had.” He added that caution must be taken because “this is very deep water – we are right on the edge of capability.” Search teams will use unmanned vehicles to navigate the depths once the search area is sufficiently narrowed to permit such vehicles’ use.

Malaysian authorities have also appeared increasingly positive in public appearances,  a change that began with the location of a frequency matching flight emergency gear. In a press conference today, acting Malaysian transportation minister Hishammuddin Hussein told the media that Malaysia was not ready to declare the aircraft lost, given the strength of the latest leads. Both Hishammuddin and Houston used the word “optimistic” in their press conferences today.

While the search for the plane itself continues, motives and details as to what happened to the plane on the night it disappeared remained a mystery. Malaysian authorities disclosed yesterday that radar pings used to locate the search area indicate that the plane deliberately navigated around Indonesian airspace so as to not get caught by surveillance in that country. CNN notes that this new route is one used by pilots, and someone with aviation experience would have had to be trained in flying in that direction; it does not appear to be a random route. 

While Malaysian authorities are unable to narrow the motive, both relatives of those on board and outsiders embroiled in the situation remain skeptical of the Malaysian government. Opposition leader Anwar Ibrahim, in particular–who personally knew the pilot of Flight 370–appeared on UK television and accused the government of covering up details, perhaps to conceal their involvement in the plane’s disappearance. Chinese relatives of those on board, meanwhile, continue to attack the Malaysian government for incompetently investigating the disappearance.