The police in Groningen cannot yet say what the exact cause is of the explosion on Wednesday on a pleasure yacht in the Meerwijck harbor in Kropswolde. Six people were injured, four of them seriously. The victims are a 28-year-old woman, two men aged 29 and 64 and three minors, all from the municipality of Midden-Groningen. One of the children is in critical condition, police said on Thursday. Forensic investigations are taking place on the ship and those involved and eyewitnesses are being heard.