SINGAPORE—A piece of aircraft wing found on an island off Tanzania in June came from the missing Malaysia Airlines Flight 370, Australian investigators said.

Experts from the Australian Transport Safety Bureau have concluded that the wing flap, found on Pemba island on June 20, originated from the Boeing Co. 777 jet registered as 9M-MRO, Malaysian Transport Minister Liow Tiong Lai said in a statement on Thursday.

Australian...