UPDATED | October 25, 2017  9:50 PM

LUCAS, Texas (CBSDFW.COM) – Two men were found deceased in a work van in Lucas on Wednesday around 4:oo p.m.

Five first responders who arrived to the scene were sent to Medical City Plano after being overcome by fumes from the vehicle.

By 7:45 p.m. they had all been released from the hospital.

bodies found in van in Lucas (CBS11)

The Collin County deputy first on the scene opened the door to check on the men who he found to be deceased, and was overcome by the fumes and taken to a local hospital with respiratory issues.

He is in stable condition.

Four Lucas firefighters were also affected by the fumes from the van and taken to an area hospital to be checked out.

Fire units have geared up in hazmat suits and are planning to pull the bodies from the van.

The Wylie Fire Chief said they still have not been able to figure out what it was that caused the two men to die and the first responders to get sick.

“Our assumption is that it was some sort of chemical reaction but you know lawn service trucks drive up and down the road every day and we are not for sure what could have happened,” said Chief Brent Parker of Wylie Fire and Rescue.

The Collin County Sheriff’s Department said it appears the van rolled to a stop in the cul-de-sac off Thunder Bay Drive and Enchanted Way.

At the vehicle, the Wylie Fire Department tested the vehicle and no chemical fumes were detected.

Firefighters think they may have dissipated when deputy left door to the van open.

They also think deputy may have inhaled most of the fumes when he opened the door.

The bodies of the two men we’re told have not even been identified yet because they haven’t been able to remove them.

A team from the Garland Health Department is assisting in trying to make the scene safe enough for the rest of this investigation to continue.