PAULSBORO, N.J. (CBS) — Fumes in the air are believed to be responsible for sending more than a dozen students and staff at a high school in South Jersey to the hospital Wednesday.

The incident happened at Paulsboro High School on N. Delaware Street in Gloucester County.

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Officials say 15 people — students and staff — were taken to area hospitals for evaluation after becoming ill.

The nearby Paulsboro refinery reported a leak in one of their tanks, which apparently sent fumes into the air. On Wednesday afternoon, the refinery released a statement that reads:

“On Monday we identified a leak on a tank containing partially-refined oil that caused an odor in the community. We immediately began addressing the leak and were in contact with local officials, including the police and school administrators. We have been taking readings and monitoring for odors in the community since Monday, with no detectable levels of hydrocarbons.

As of this morning we had removed most of the remaining material from the tank. We tested the roof of the tank with a monitor and measured no detectable results. We are also checking other areas of our operations for potential sources.

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We will continue to work with local officials, including school administrators, to understand the issues of concern today.”

Fire and hazmat crews were at the high school.

Paulsboro Police say school officials made the decision to close the high school for the remainder of the day to give fire department and county hazmat officials time to air out the building.

No other schools were impacted, but police say air quality monitoring will be taking place throughout the rest of the day to ensure the safety of students and staff.

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The incident remains under investigation.