Edison, NJ – WABC, By Anthony Johnson- A school in Edison, New Jersey remains closed as investigators try to track down the source of a carbon monoxide leak. The leak made more than a dozen students sick.

So far the water has been tested, the air has been tested and so has the food – but the source of the carbon monoxide leak remains a mystery.

Only a couple of people entered the school, which is on virtual lock-down while authorities try to determine the source of the apparent carbon monoxide leak that forced about a dozen students to be treated on the scene while others were hospitalized.

Officials say they haven’t found the source of the problem but Wednesday testing showed everything was normal. That testing will continue, but in the meantime the 250 students evacuated from the school will remain out of the building until next Tuesday.

Chief Robert Campbell, Edison Fire Department: “We will go back every day – Thursday, Friday, Saturday, Sunday, Monday – and test the building again to see if we can determine if this problem was caused by an internal source.”