COLLIN COUNTY, Texas -- A strange odor is being investigated in Luca, Texas after two people were found unconscious inside a van early Wednesday evening.

A Collin County sheriff's deputy and four firefighters were called to check out the van, which belonged to a lawn care company, at about 4 p.m. Wednesday.

When they opened the door, they were overcome by a strong smell of ammonia. They had skin irritation, chest pain, nausea, and a dry cough, officials say, and were sent to the hospital to be checked out. They have all since been released.

HazMat teams were called to the scene and found different chemicals during a reading. However, nothing was over the limit as far as being hazardous. No chemicals were labeled as ammonia, although that's how the smell is being described.

The two people inside the van, believed to be employees of the lawn care company, were pronounced dead. They haven't been identified.

Officials say the ambulance and other equipment involved in the investigation will have to be de-contaminated due to the chemicals.

Residents nearby were told to shelter in place, but no one was evacuated.