The NSTB report drew no conclusions on the cause of the problem, and kept its report "docket" to the facts in the investigation so far.
The report focuses on a Jan. 7 incident aboard a Japan Airlines Boeing 787-8, when smoke was discovered by cleaning personnel in the aft cabin. The 787 was parked at a gate at Boston Logan International Airport.
A mechanic found smoke and flames coming from the airplane's lithium-ion auxiliary power unit battery in the aft electronic equipment bay. Aircraft rescue and firefighting personnel responded to the fire, which resulted in one minor injury to a firefighter, the NTSB said.
"Because the investigation is continuing, no conclusions or recommendations are being made at this time," the NTSB report said.
"The NTSB's investigation into the probable cause of the 787 battery fire at BOS is continuing," the report said. "The NTSB is also continuing to review the design, certification and manufacturing processes for the 787 lithium ion battery system."
The report said "external observations" of the battery showed, "among other things, that the right side of the battery case appeared to have the most extensive damage of the four battery sides. Disassembly of the battery revealed that the cells that were located in the left side of the battery ... generally exhibited the least thermal and mechanical damage and that the cells that were located in the right side of the battery exhibited the most thermal and mechanical damage."
The report also cited concerns by the Federal Aviation Administration that the 787 incorporated "novel or unusual design features," including the lithium-ion batteries.
Besides the Boston 787 incident, on Jan. 16, Japanese carrier All Nippon Airways had to make an emergency landing after receiving a warning of a battery failure. Japan's Transport Safety Board has been investigating.