Sicilian authorities have ordered the closure of the Macalube nature reserve after a seven-year-old girl was killed in an explosion of a small mud crater.
Police said the girl, her brother and father were buried in mud and sediment when one of the craters exploded in western Sicily. The nine-year-old boy is missing while the father is being treated at a hospital.
The phenomenon is the result of methane gas mixing with salt water and clay.
The director of the reserve, Mimmo Fontana, was quoted as saying that a project to monitor the volcanic system had never been launched due to a lack of funding.