DALLAS (CBSDFW.COM) – Two adults were arrested Sunday afternoon after police say they left four children locked in their car with a window cracked for more than two hours while they donated plasma.

As the temperature inched closer to 100 degrees, Dallas police say they responded to a parking lot on the 1300 block of N. Masters where they found the children – a 2-month-old, a 15-month-old, a 3-year-old, and a 5-year-old – overheated and listless.

"It's sad," said Brandon Finley, who said he saw the children drenched in sweat. "Like they just got out of a pool … about to pass out."

Paramedics gave the children water and drove them to Children's Medical Center, where all four were reported to be in stable condition.

"They were just real sweaty and pretty upset," said Brian Malouf, a paramedic with Dallas Fire Rescue.

Dallas police, meanwhile, arrested two adults – Natasha Hamalian, 22, and Nicholas Madison, 24 – for abandoning and endangering a child in "extreme heat."

Witnesses say the pair were visiting CSL Plasma, a clinic where they could sell the plasma in their blood for cash.

A police report shows the children may have been in the car from as early as 10:34 a.m. until officers arrived at 12:44 p.m.; more than two hours later.

Witnesses say someone had left a window cracked, but turned off the car itself.

Under those conditions, paramedics say the heat can quickly overwhelm young children.

"The temperature outside may be a 100, but inside the car it could be a 120 degrees in there. Little children can't compensate like adults - and they get a lot worse, a lot quicker," said Malouf.