Tokyo’s Haneda airport closed one of its three runways for about 40 minutes Monday after an outer fence was found to be partly unraveled, the airport operator and police said.

Shortly before 5 p.m., a security guard found the roughly 50-cm diameter opening in the wire fence dividing the airport from the outside. There is no sensor in the area. The opening began near the ground and was apparently made by the fence being unraveled by hand, they said.

The runway nearest the damaged west side fence was closed while the operator confirmed that no trespassers had entered. No flights were delayed.

A security company reported the hole to the airport operator, but the operator’s employee arrived at the site nearly an hour later, they said.

The security company’s staff noticed nothing unusual while watching over the site between around 10 a.m. and 11 a.m.

The airport’s security system was thrown into question when the airport was forced to close temporarily April 28 after a man burst onto the runways in a stolen car before eventually jumping to his death in Tokyo Bay.