Officials say they have a few leads in their investigation into who brought at least a quarter-cup of mercury to a Las Vegas middle school.
One student's home was found to be contaminated with the element, but Environmental Protection Agency officials have now cleaned the home and police say there is no indication that the student who lives at the contaminated home was the one who brought the substance to Walter Johnson Junior High School.
Mercury was first found at the school just before noon on Sept. 6, prompting a screening for 1,200 students that lasted for 17 hours.
Capt. Ken Young says police hope to identify the person or people responsible by the end of the week.