LACEY — Potentially high levels of mercury have forced a second New Jersey school to close its gymnasium early in the school year.

A letter by schools Superintendent Vanessa Clark sent to Mill Pond School parents said the district has been working to address the mercury levels in the school's gym over the past week. While the levels of mercury detected have been determined to "not pose a threat" to the health and safety of students and staff, the decision was made to close the room.

So far, the district's indoor air quality consultant has taken air samples in the room, Clark said. The consultant will now take samples of the gym floor surface to check the mercury levels in the floor. Clark said it may take "up to a week" to get the results of the test.

"I know that it is somewhat inconvenient to not have access to the gymnasium; however, we always want to react to a situation in a manner that prioritizes the safety of our students and staff," Clark said in the letter.

While the gym is closed, Clark said students will have gym class outside weather permitting, or in classrooms that will "permit maximum movement."

In her letter, Clark noted that schools across the state have been notified that "certain synthetic floors installed between 1960 and 1980 may contain mercury and that this mercury may emit a vapor into the air." The floor in the gym was installed in 1980, the school said.

Earlier this month, officials in Freehold Township announced they were testing the gym at the Joseph J. Catena School for mercury levels, according to the Asbury Park Press.

Clark encouraged anyone with questions about the situation to contact her directly.