A panel weighing around 4 kg fell off a plane shortly after takeoff Saturday at Kansai International Airport and hit a car on a road in Osaka, the transport ministry said.

No one was injured by the object. The ministry will send safety inspectors to look into the cause of the mishap, officials said.

The panel, about 60 cm long and 1 meter wide, fell from a KLM Royal Dutch Airlines plane that took off at 10:40 a.m. Saturday for Amsterdam, according to the Osaka bureau of the Land, Infrastructure, Transport and Tourism Ministry.

The panel struck the window of a car at about 11 a.m. in central Osaka as it was driving past shops and apartment buildings but did not injure the two female occupants, who eventually called the police, the bureau and other sources said Sunday.

KLM found the panel was missing after the plane arrived in Amsterdam later Saturday.

According to the ministry, the plane was a Boeing 777 with 321 passengers and crew aboard. The panel is believed to have fallen off while the aircraft was flying at an altitude of 2,400 meters or higher.

The panel is made of nonmetal compound materials and is part of the base of the right wing. No abnormalities were reported on the plane during pre-departure checkups.

"KLM regrets this incident and has immediately launched an investigation into the causes," the airline said, adding it is "in close contact with Japan's civil aviation authority and Boeing on this matter."