AVONDALE, Ariz. -- Mercury contamination at a valley high school turns out to be more widespread than officials first reported.

Friday afternoon, an Environmental Protection Agency official said belongings from at least 50 people at Agua Fria High School tested positive for mercury.

Their homes will now be screened for the substance.

“Our goal with that,” said EPA coordinator Michelle Rogow, “is to close the loop on this and to minimize the exposure and the contamination and to reduce their risk.”

So far, clothes, shoes, and other items from 500 students, staff, and teachers at the school have been screened for the dangerous metal. Items from 40 more people have yet to be tested.

Rogow said, “We’re really in an information gathering phase right now.”

She also said it’s unclear at this time how many students could suffer serious health effects from their exposure to the dangerous metal.

Although, Rogow said, when five students took the metal from a classroom last Thursday and brought it home, they contaminated several locations along the way.

Rogow also said, “a few classrooms in the school, a locker room and some buses were contaminated with mercury.”

She went on to say, “those areas had levels of mercury in them, mercury on the floors, mercury in the seats, in various locations.”

CBS 5 sources say two science teachers are now substitute teaching at other Avondale district schools because of the incident.

Our sources also say the teachers are teaching subjects other than science.

The sources say the teachers may be to blame for leaving the mercury where students could find it.

We knocked on the door of one of the teacher’s homes Friday night. No one answered.

One of her students at Agua Fria High School told us she was gone Thursday afternoon, when classes resumed.

Zach Lamonaco said, “as soon as I came back, my science teacher was gone, and she’s like no where to be seen.”

The school was closed from Friday February 13 through February 18 while the building was decontaminated.

The Avondale Assistant Superintendent would not confirm or deny whether the two science teachers had been moved to other locations.

She did say the EPA and other agencies, including Avondale police and fire are working together to investigate the incident.

However, the EPA said it is waiting for the school district to finish its own internal investigation before it begins looking into the mercury contamination.

The agency said breathing in mercury vapor can have negative health effects. Symptoms depend on how much and long you breathe mercury vapors.

Short-tem exposure to high levels of mercury can cause cough, sore throat, shortness of breath, chest pain, diarrhea, nausea, vomiting, headaches, eye irritation, vision problems, an increase in blood pressure or heart rate, and a metallic taste in the mouth.

The effects of long-term exposure include anxiety, loss of appetite, tremors, and vision and hearing changes.

The EPA encourages anyone at Agua Fria High School, who is concerned about their exposure to mercury, to see their doctor.

Urine and blood tests can quickly reveal if a person has been exposed to an unsafe level of mercury.