LAS VEGAS — The U.S. Environmental Protection Agency is doing additional testing of 10 bags of clothing belonging to students at a Las Vegas school where several drops of mercury were discovered.

Clark County School District spokeswoman Melinda Malone said Saturday that the EPA has already cleared more than 700 bags of items left at Walter Johnson Junior High since Wednesday’s discovery.

EPA staff has also gone through bags of clothes that 50 families brought to the school. They will continue to accept items until 9 p.m. Sunday.

The agency also visited eight homes and found no evidence of contamination prior to the mercury discovery.

Crews are cleaning the gymnasium and locker rooms.

Authorities kept 1,200 students for up to 17 hours to screen for exposure, drawing outrage from parents.