"During the search we located a compartment built in the gas tank of this vehicle, and inside the gas tank was a modified tank which had roughly 25 pounds or 3 gallons of liquid fentanyl," explained Mike Tamez with the Nueces County District Attorney's Criminal Interdiction Unit.How the liquid fentanyl was hidden -- and later foundTamez said a number of things caused the deputy to believe something was not right.But this liquid didn't crystallize when hitting the open air like meth does, and it later tested negative for meth.Largest liquid fentanyl drug bust"When we spoke with our federal partners to help us with this case the one commonality was that they never heard of this much liquid fentanyl ever being hit on a traffic stop on a Texas highway," Tamez said.The scene wasn't clear until 7 p.m.Tamez said this drug bust will make a difference because fentanyl overdoses continue to surge both in Nueces County and nationwide."