An explosion at a waste water company’s yard in Ventura County overnight caused minor injuries to dozens of people and closed Highway 126 for a number of hours on Nov. 18.

The explosion at the Santa Clara Waste Water Treatment Plant in Santa Paula happened while a truck was pumping waste from a collection tank, according to Sgt. Denise Sliva of the Ventura County Sheriff’s Department. No one was seriously injured but a total of 34 people were treated, mainly for irritation to the eyes and other respiratory symptoms the sheriff’s department said. The origin of the explosion and the substances involved were still under investigation, and a hazardous materials team was deployed to the site.

Highway 126 was closed in both directions for more than six hours. The incident was in the cleanup phase by 5 p.m., the sheriff’s department reported. Press reports put the number hospitalized at as many at 46.