Law officers also were on alert in northern Utah and neighboring states. Both men have family in the Logan and Ogden areas.
Laursen said he believes the two are long gone from his county.
"We don't think they're still here, but we're still looking everywhere we can think of in the county," he said.
Derrick is serving a sentence for second-degree felony burglary, third-degree felony theft, third-degree felony possession and/or use of a controlled substance, third-degree felony failure to stop or respond at the command of police, and class A misdemeanor child abuse, Utah Department of Corrections spokesman Steven Gehrke said.
Braham was behind bars for second-degree felony burglary, second-degree felony theft, third-degree felony theft, third-degree felony burglary and class B misdemeanor theft, Gehrke added.
Laursen said the escape is believed to have taken place at 1 a.m. while the two inmates ostensibly were working in the laundry.
"I guess they thought it was just time," Laursen said. "They had been planning it for a while, since they had to find a way to get behind our two big industrial dryers and then into the vents."
Gaining exit from the area was not simply a case of kicking out a vent, as initially reported, however.
The vents, with 3-by-2-foot openings, had security screening in addition to a vent screen. "It took them a little work to get through those. We didn't think anyone could," Laursen said.
The inmates also had to first defeat a security door and avoid notice of monitors covering the laundry room and adjacent, restricted space where supplies are stored. How they managed that, with six jail staffers on duty at the time, was under investigation, Laursen said.
The two were not reported missing until a 2 a.m. jail head count turned up two short.
Once through the vent, the inmates fled through the jail's parking lot and, half a mile away, found the Yukon its keys in the ignition and with a full tank of gas parked at a Vernal home.
That, too, was being investigated, though it appeared initially to have been an oversight by the vehicle's driver.
The escapes Wednesday were reminiscent of another jail break by state prisoners from a rural county jail. In 2007, on a Sunday afternoon, convicted murderers Danny Gallegos and Juan Diaz-Arevalo went over the fence at the Daggett County jail. The pair were recaptured six days later near Rock Springs, Wyo.
Laursen said Uintah County Jail has 150 inmates on hits roster, 29 of them including the escapees who are being housed for the state prison system.
Laursen said Wednesday that police in Wyoming, as well as Colorado, Idaho and Nevada , also were on the lookout for Derrick and Braham. However, unlike Gallegos and Diaz-Arevalo, neither of Uintah County's escapees has a violent background, Laursen said.
"They've been pretty good kids here, actually," Laursen said. "This all is kind of a surprise to us."
Anyone seeing the escapees, or anyone with information related to the two, is asked to call 911 immediately. Callers also may contact Uintah County Undersheriff John Laursen at 435-621-6092, or by email at email@example.com.