Police are searching for a mother and newborn baby after finding evidence she may have given birth by a Sydney riverbank. Emergency services were called to Cooks River at Earlwood in the city’s south-west on Monday afternoon after a resident walking his dog found what police believed to be a placenta and umbilical cord. Police said tests on the organs revealed them to be human. Serious concerns were held for the welfare of the child and mother and detectives established a crime scene, and launched an investigation into the incident. Sign up for Guardian Australia’s free morning and afternoon email newsletters for your daily news roundup Police urged the mother to attend her nearest hospital to receive urgent care. Supt Christine McDonald said lights were brought in to allow the launch of a large-scale search on Monday night. The search was due to resume on Tuesday morning, police confirmed. “Obviously our search will hopefully identify what has taken place; whether the delivery of that child occurred at this location or another location is yet to be determined,” she said. “I ask anyone with information to contact Crime Stoppers. “It’s very important and it’s extreme urgency we find the mother and the child as soon as we can. We ask she goes to a hospital. We will be contacting hospitals.” The Cooks River flows from Yagoona in Sydney’s outer south-west and runs into Botany Bay at Kyeemagh, 23km away. Anyone within the vicinity of Lang Road, Wardell Road, Ewen Park and Tennent Parade on Monday who may have seen a woman in distress was urged to come forward. “Any information is critical,” McDonald said, with police also appealing for CCTV footage. Whether police search the river itself would be “dependent on what we find as the search continues”, McDonald said, with police divers also “a possibility”. “To be honest I hope that the mother and child present themselves before any of that has to be undertaken.”