Stenciled codes on two debris pieces found along the coast of the southeast African nation of Mozambique "almost certainly" prove they originated from missing Malaysia Airlines Flight MH370, the Australian Transport Safety Bureau (ATSB), which is leading the search for the plane, said in a report Tuesday. Over the last few months, four pieces of debris possibly from the missing plane have been recovered, including one each from South Africa and Mauritius.

The two items from Mozambique, which were found on Dec. 27, 2015, and Feb. 27, 2016, were sent to Australia for examination at the request of the Malaysian government. ATSB said Tuesday that one of the pieces — found in Mozambique in late December by a South African teenager holidaying with his family — is a "segment from a Boeing 777 flap track fairing." The second piece — found in late February by U.S. blogger and lawyer Blaine Gibs — is "a segment of a Boeing 777 RH horizontal stabilizer panel."

Investigators revealed that the stenciling of the code “676EB” and the words “NO STEP” on the debris provided almost irrefutable evidence that the parts were from the missing Boeing 777.

Mozambique debris 1 Flap fairing outer surface showing stencil location and comparison. Photo: Australian Transport Safety Bureau

"The 676EB stencil font and color was not original from manufacture, but instead conformed to that developed and used by MAB during painting operations," investigators said in the report. The stenciling of "NO STEP" was also "consistent with that developed and used by Malaysian Airlines."

Mozambique debris 2 Stabiliser panel “NO STEP” stencil and fastener comparison. Photo: Australian Transport Safety Bureau

The two debris pieces will be sent to Malaysia this week for further examination, ATSB said in the report.

Australian authorities also said that two other items — the South Africa piece with the Rolls Royce logo and the piece found on the Rodrigues Island in Mauritius — were brought to ATSB laboratories last week.

"Investigators from the ATSB and the Malaysian authorities are currently examining those two pieces for details which would serve to identify them as coming from a Boeing 777, and in particular for any details which might serve to link the debris as coming from MH370," authorities said.

The ongoing search for Flight MH370 — which went missing on March 8, 2014, with 239 people on board while on its way from Kuala Lumpur to Beijing — has not yielded any concrete clues about what happened to the jet.

In July 2015, a flaperon belonging to Flight MH370 turned up on the French-controlled Réunion Island in the Indian Ocean.

The underwater search in a remote part of the southern Indian Ocean has cost nearly $70 million, with four vessels still scouring the ocean floor to find the plane wreckage. The search operation, which has been headed by Australia, is expected to be called off in June.