Staff and children at a school in Tokyo on Wednesday took part in a test of a device designed to prevent children from being left in school buses.

The test came after a 3-year-old girl died from heatstroke last week when she was left in a school bus in Shizuoka Prefecture, central Japan.

The Tokyo-based company Octo is developing the device with the aim of commercializing it.

The device triggers a buzzer when the driver turns off the engine. It keeps sounding until a button on a seat at the back of the bus is pushed. The device is expected to increase the chances that the driver will notice any children left in the bus.

The test was conducted on Wednesday at Hillock primary school in Tokyo's Setagaya Ward using a school bus. School staff, including a driver, and children took part in the test and confirmed how the device worked.

Octo President Adachi Ryohei said he was able to learn children's behavior patterns and how much time it takes for them to get on and off the school bus. He added that his company will listen to what drivers and others have to say about the device and improve it.

Hillock School Director Minote Shogo said the death of the girl in Shizuoka Prefecture is an issue that concerns him because his school is also entrusted with children. Minote said the device was easy to use and effective, but checks by humans are necessary because it could malfunction no matter how much technology advances.