CHAPEL HILL — A dangerous mixture of chemicals was found in a dumpster behind Chapel Hill High School Thursday. Four people were treated and released from the hospital. They suffered from eye irritation and headaches.

The deputy fire chief says someone dropped off a dangerous combination of chemicals near the dumpster at Chapel Hill High School.

Workers using a fork lift punctured the 55-gallon drum when they tried to put it in the dumpster. A maintenance worker discovered the spill about 9 a.m.

Four people were rushed to the hospital complaining of trouble breathing and burning eyes.

"Since we were unable to determine what the product was, we have evacuated the area and have contacted the Parkwood Regional Hazmat team. They have suited up," said Fire Marshall Caprice Mellon.

The Hazmat team figured out what the chemicals were and changed into cocoon suits -- the most protective suits they have.

One chemical was a pesticide, and another one was a diesel solvent.

"The other one is Chloropicrin which is one of the ingredients in tear gas. That would explain why the gentlemen who went to the hospital were complaining that their eyes were burning," said Dep. Chief Robert Bosworth.

Crews removed the chemicals after a careful, five-hour operation.

School does not start until next week, but teachers in for a work day were kept away from their cars most of the day.

"Had this been a regular day, then we would have had parents all down the highway trying to get the students. If this had to take place, it was better that it took place today," said Principal Carlotta Armstrong.

The school system says they can't believe someone would leave something like this behind.

"Complete, absolute irresponsibility. [They were] trying to get something they couldn't get rid of any other way and they are going to let us take care of it. To drop it off next to a school is beyond our understanding," says Dave Tinker, a spokesperson for Chapel Hill/Carrboro Schools.

The four people who were taken to the hospital were treated and released.

The waste was a mixture of at least three chemicals. One of the chemicals was Ethylene Dibromide which is described as an insecticide.

Chloropicrin was also present. That is an eye irritant and is one of the ingredients in tear gas.

There was also a diesel solvent in the mixture.

Authorities have no idea why the chemicals were combined, but they speculate that the chemicals could be used as a pesticide.