Narita airport closed one of its two runways around noon Wednesday after three people were spotted near a taxiway, the airport operator said.
The runway reopened 10 minutes later after the three were found to have had permission to conduct a survey of bird life in the area, according to Narita International Airport Corp.
The airport operator said the crew of a KLM Royal Dutch Airlines flight from Amsterdam spotted the three near the taxiway and reported it.
The airport authority said it is investigating why the three were in that location.