A U.S. prison guard charged in connection with the escape of two killers admitted providing them with tools, paint, frozen hamburger meat and access to a catwalk electrical box, but claims he never knew they planned to bust out, authorities say.

As the search for the convicts entered its 20th day Thursday, Gene Palmer was released on $25,000 bail after his arrest on charges of promoting prison contraband, tampering with evidence and official misconduct. His arraignment was postponed until Monday.

Palmer is the second Clinton Correctional Facility employee to be charged since two convicted murderers, Richard Matt and David Sweat, cut their way out of the maximum-security prison in far northern New York, close to the Canadian border, on June 6. A prison tailor shop instructor Joyce Mitchell, 51, is charged with helping them break out.

But in contrast to the allegations against Mitchell, Palmer said he was an unwitting helper.

Prison escape

New York State Police have been searching for escaped killers David Sweat and Richard Matt since June 6. (New York State Police/Getty Images)

"I did not realize at the time that the assistance provided to Matt or Sweat made their escape easier," he told authorities in a signed statement.

District Attorney Andrew Wylie said that based on Palmer's statements and a polygraph test, investigators have no reason to believe he was knowingly involved in the escape.

In the statement, Palmer admitted providing Matt with paint and paintbrushes. On four occasions over eight months, he supplied Sweat with needle-nose pliers and a screwdriver. He said he gave Sweat access to the catwalk later used in the escape to change the wiring on electrical boxes as "a favour" to make it easier for them to cook in their cells. And a week before the escape, he delivered to Matt a pound of frozen ground beef in a package left by Mitchell.

Palmer told investigators that he agreed to help the pair in return for information about some illegal acts the other inmates were engaged in.

Wylie said Mitchell told investigators she smuggled hacksaw blades, a screwdriver and other tools into the prison by hiding them in the frozen meat.

She then put the meat in a refrigerator in the tailor shop, and Palmer took the meat to Sweat and Matt, who were housed in a section where inmates are allowed to cook their meals, according to the district attorney.

Palmer to plead not guilty

Wylie said Thursday that investigators have no proof Palmer knew hacksaw blades were embedded in the meat.

Palmer, who has been suspended, will plead not guilty, according to his lawyer.

Authorities say the inmates cut through the steel wall at the back of their cells, crawled down a catwalk, broke through a brick wall, cut their way into and out of a steam pipe and then emerged from a manhole outside the prison.

Sweat, 35, was serving a life sentence without parole in the killing of a sheriff's deputy. Matt, who turned 49 on Thursday, was doing 25 years to life in the kidnapping, torture and hacksaw dismemberment of his former boss.

Palmer had worked at the prison in Dannemora for more than 27 years and had known Sweat and Matt for at least five years.

In a 2000 interview with a local radio station, Palmer portrayed his job as highly stressful.

"With the money that they pay you," he said, "you'll go bald, you'll have high blood pressure, you'll become an alcoholic, you'll divorce, and then you'll kill yourself."

About 1,100 law enforcement on Thursday continued their search for the escaped convicts.