Transport ministry officials suspect the scorching heat wave was the cause of a hole found in a runway at Tokyo's Haneda Airport.
The hole -- about 20 centimeters long, 30 centimeters wide and 10 centimeters deep -- was found in one of the airport's 4 runways on Monday. The runway was closed for about 4 hours, disrupting flight operations.
Ministry officials say heated water may have expanded the asphalt and weakened the paved surface.
They say an inspection of the runway on Monday night through Tuesday found that the pavement around the hole had deteriorated, and warned that additional cracks could occur.
The ministry completed the repair of a section of the runway 60 meters long and 5 meters wide by early Wednesday morning.
Many areas across Japan are suffering from a severe heat wave this month.