The aircraft’s cockpit voice recorder, discovered at the mountainous crash site in the Guangxi province, has been transferred to a National Transportation Safety Board (NTSB) facility in Washington, according to the agency. U.S. specialists are assisting investigators from the Civil Aviation Administration of China (CAAC) as they attempt to glean crucial details about the run-up to the tragedy.

An NTSB crash-investigation team also left Friday headed for China to assist the investigation.

“Investigators will limit interactions with those outside of investigation similar to safety protocols at Beijing Olympics, which will allow them to begin work immediately without a quarantine,” the agency said.

Aviation safety experts said the type of Boeing aircraft that went down, the 737-800, is widely used globally and has had a strong safety record. China has also improved its safety record in recent decades. Its last major crash occurred in 2010, when pilots missed a runway in heavy fog, killing 44 people.

The CAAC said this week that it is continuing a nationwide inspection effort following the China Eastern crash “to further strengthen awareness of bottom lines and to troubleshoot safety hazards in the civil aviation field, so as to guarantee higher level safety of aviation operations and people’s lives.”