A nationwide manhunt intensified Wednesday for two Georgia inmates who allegedly shot and killed two correctional officers before escaping in a stolen car early Tuesday morning.

The Georgia Bureau of Investigations and the FBI are now offering a combined $90,000 reward for information leading to the arrest of Ricky Dubose and Donnie Rowe, officials said.

Escaped prisoners Rowe and Dubose stole a white 2008 Ford F-250, GA tag BCX5372, overnight. Their direction of travel is unknown. pic.twitter.com/0VHz93t6Rv — Athens-Clarke Police (@accpolice) June 14, 2017

Dubose, 24, and Rowe, 43, allegedly overpowered and killed Georgia Department of Corrections officers Christopher Monica and Curtis Billue while they were on a bus transporting inmates.

At a press conference Wednesday, Putnam County Sheriff Howard Sills said he was frustrated that the suspects have managed to elude law enforcement.

"My professional opinion is that probably, they're not in the area, but I couldn't guarantee that," he said. "Two correction officers have been murdered — it's very frustrating."

Sill said the suspects are now believed to be traveling in a white two-door Ford pickup truck that was reported stolen from an industrial site less than 10 miles from the sheriff's office. He said the truck has not been spotted since it was reported as missing.

Authorities are also looking for the green Honda Civic that the inmates allegedly carjacked to flee from the scene of the shooting.

"Obviously they're doing pretty good," Sills said. "They stole two vehicles in the last 30 hours so, obviously they've got to have gas and things so I assume they've acquired some money somewhere."

Related: Two Georgia Inmates on the Run After Killing Correctional Officers

The fugitives are still believed to be armed with the 9 mm pistols that they allegedly took from officers after the shooting. Sills urged the public to study the latest photos released of Rowe and Dubose, taking particular note of crown tattoos above Dubose's eyebrows.

"They're dangerous criminals. And and we need the public's help in locating these vehicles and locating these individuals," Stills said. "They just murdered two corrections officers in a brutal fashion. They're not concerned with anything regarding human life."

Flags were lowered to half staff on Wednesday to honor officers Monica and Billue. Monica had been with the force for more than seven years and Billue had served for nearly a decade, according to police.

Sills said he could not rule out if the suspects had split up in the hours since the shooting. They were last seen near a Family Dollar store in Madison, Georgia, Tuesday afternoon.

GBI Director orders flags to be lowered to half staff in honor of the memory of Officers Monica and Billue. #LODD pic.twitter.com/rH5NZVvfGD — GA Bureau of Invest (@GBI_GA) June 13, 2017

Rowe and Dubose were being transported from a state prison early Tuesday when the inmates allegedly broke into the locked area of the bus separating the guards from the prisoners, shot and killed both officers, took their 9 mm handguns, and then carjacked the first vehicle to approach the scene.

Authorities said it is too early to determine if changes will be made to how Georgia inmates are transported.

Rowe is serving a life sentence with no parole for armed robbery and Dubose was behind bars for 20 years for armed robbery. Both inmates were housed at Baldwin State Prison, the state Department of Corrections said.