Two dogs have died after ingesting an “unknown white substance” at a park in Liverpool. Merseyside Police have cordoned off a green space close to Childwall Valley Road after reports emerged of four dogs falling ill after eating a strange substance. The animals were taken to a veterinary surgery at around 2.00pm on Monday. Two have since died, whilst a third is seriously ill. The fourth is continuing to receive treatment. People have been told to stay away from the cordoned-off area, whilst tests are being carried out to establish what the substance is. It will then be removed in a “safe and c…