Japanese airline ANA Holdings said on Wednesday that it had found an electrical wiring problem in the fire extinguishers of the engines on three Boeing 787s.
An assembly error at its service center impacted some refurbished fire extinguisher bottles, a United Technologies spokesman said in an email.
"This error has been corrected and we are working with Boeing and the airlines to complete the necessary inspections, which we expect will be completed over the next few days."
Japan Airlines also said on Wednesday that it was inspecting its Dreamliner fleet for similar problems.
The Wall Street Journal reported late on Thursday that the bottle-assembly at a Boeing supplier facility was responsible for the faulty fire systems.