SAN FRANCISCO (AP) – A U.S. judge in San Francisco says evidence seems weak that Roundup weed killer causes cancer, but experts can still make that claim at trial. The ruling Tuesday by U.S. District Judge Vince Chhabria allows hundreds of lawsuits against Roundup’s manufacturer, Monsanto, to move forward. The lawsuits by cancer victims and their families say the agrochemical giant long knew about Roundup’s cancer risk but failed to warn them. Many government regulators have rejected a link between the active ingredient in Roundup and cancer. Monsanto has vehemently denied such a connection. The judge wanted to determine whether the science behind the claim that Roundup can cause non-Hodgkin’s lymphoma had been properly tested and met other requirements to be considered valid. He spent a week in March hearing from epidemiologists and other doctors.