Federal investigators have so far been unable to break into the phone of Devin Patrick Kelley, the suspect in Sunday’s deadly church massacre in Texas, which is setting up a possible encryption showdown with technology companies.

According to Christopher Combs, FBI special agent in charge, the authorities have been unable to get into Kelley's phone due to encryption. That problem could rekindle a battle that gained national attention after Apple refused to help federal investigators break into an iPhone used by Syed Farook, the shooter who killed 14 in San Bernardino, Calif., in 2015.

“It actually highlights an issue that you’ve all heard about before, with the advance of the technology and the phones and the encryptions," Combs said at a press conference Tuesday. "Law enforcement — whether that’s at the state and local or at the federal level — is increasingly not able to get into these phones.”

Combs declined to reveal what type of cellphone Kelley owned.

Kelley, 26, opened fire at First Baptist Church in Sutherland Springs, Texas, on Sunday, killing 26. He fled and was found dead from an apparent self-inflicted gunshot wound. Kelley was a former member of the Air Force who was dishonorably discharged and had a violent past.

Combs said the FBI is working to get into the phone, and that efforts “will continue until we find an answer.”

“I don’t know how long that’s going to be,” he added.

Last month, the Department of Justice hinted that it is ready to reignite its battle with major technology companies over encryption. Deputy Attorney General Rod Rosenstein said in an October speech to the U.S. Naval Academy that technology companies’ encryption software enable criminals.

"When investigations of violent criminal organizations come to a halt because we cannot access a phone, lives may be lost," he said. “The approach taken in the recent past, negotiating with technology companies and hoping that they eventually will assist law enforcement out of a sense of civic duty, is unlikely to work," he said.

According to Rosenstein, the FBI was unable to access roughly 7,500 devices seized in investigations in 2016.

Apple in 2015, and other major technology companies since, say creating a “back door” around encryptions can allow bad guys to hack and steal information and content.

The FBI eventually paid a company nearly $1 million for a “tool” to break into Farook’s phone.