A popular national forest in California has closed trails near where a couple, their baby and the family dog were found dead last month. Pointing to “unknown hazards found in and near the Savage Lundy trail”, officials announced Sierra national forest would close trails, campgrounds and picnic sites for nearly a month. John Gerrish, 45, his wife, Ellen Chung, 30, their one-year-old daughter, Muji, and their dog were found dead on the Mariposa county hiking trail. Officials have not yet been able to determine how they died. Officials found the bodies of the family, who had reportedly gone out for a hike, on 17 August after a family friend reported them missing. With no signs of death immediately clear, the Mariposa county sheriff’s office briefly treated the area as a hazmat site. Investigators initially explored whether carbon monoxide, exposure to gas from mines in the area or toxic algae could have been responsible for the deaths. Prior to the tragedy officials had warned hikers of harmful algae blooms along the south fork of the Merced River, and a water test in the area was positive for toxic algae, the San Francisco Chronicle reported. The state water board and independent labs are also testing water the family had with them. The closure, which is in effect through 26 September, came the day before the US forest service announced it would close all of California’s national forests through 17 September due to the state’s wildfire crisis. The majority of trail has little shade and trees, and temperatures were as high as 109F the day the family went hiking. The sheriff’s office announced last week it had ruled out guns or any other types of weapons and any chemical hazards along the trail as causes of death. Autopsies on the family have been completed, but officials are awaiting toxicology results. “We know the family and friends of John and Ellen are desperate for answers, our team of detectives are working round the clock. Cases like this require us to be methodical and thorough while also reaching out to every resource we can find to help us bring those answers to them as quickly as we can,” Jeremy Briese, the county sheriff, said.