ANGOLA, La. (AP) — Snapshots of illegal drugs, homemade knives and other prohibited items found on inmates, visitors and staff at the Louisiana State Penitentiary cover the security office walls.

Lt. Joseph Russell’s pictures illustrate a problem faced by prisons nationwide — keeping contraband out and finding forbidden items that already have made their way in.

It is impossible to keep out all contraband, experts say. Louisiana, which implemented extensive court-ordered prison reforms in the 1970s and 1980s, does a better job than most, said Jim Gondles, executive director of the American Correctional Association.

‘‘Angola is a picture-perfect example of how their system has turned around,’’ Gondles said.

Angola was known as the nation’s bloodiest prison before federal courts forced changes. Louisiana is now one of only 14 states whose prisons are fully accredited by the corrections association, Gondles noted.

The state has just under 20,000 inmates in 11 state-run and two privately managed prisons. Accreditation certifies that they meet national standards set by corrections experts.

But even well-run prisons confront problems with contraband.

‘‘It’s like fishing, you can’t catch them all,’’ Angola Warden Burl Cain said.

According to statistics compiled by the Louisiana Department of Public Safety and Corrections, illegal drugs were found inside state prisons 1,265 times from 2006 to 2008.

During the same three-year period, 1,402 urine tests showed inmates had taken drugs.

The prison system conducts more than 40,000 such tests each year, records show. Most are random, but others are based on ‘‘reasonable suspicion’’ that an inmate might be using drugs.

Most positive tests — 1,167 — registered for THC, the active chemical in marijuana. There also were 71 positives for cocaine, 30 for amphetamines, and 119 for other drugs, according to prison data.

Jeff Travis, chief of operations for the corrections department, said drugs find their way into Louisiana’s prisons a variety of ways.

For example, he said, an outside accomplice might tape a packet of drugs to the back of a street sign for an inmate on a work crew, or leave drugs in an empty soda can along the highway.

‘‘When you’ve got a bunch of inmates trying to beat you, a little bit gets by you sometimes,’’ Travis said.

One inmate had a friend tape marijuana to a paper airplane and sail it across a double security fence and onto prison grounds, said Steve Rader, warden of Dixon Correctional Institute in Jackson.

‘‘There’s a lot of guys that like to smoke marijuana and will pay whatever they have to pay to get it in,’’ Rader said.

Drug-sniffing dogs, cell and dormitory shakedowns and inmate strip-searches are used to keep contraband out of the prisons. So is sophisticated technology, such as ion scans that can detect the slightest trace of drugs, he said.

‘‘Even in the most high-tech, high-security prisons in the country, contraband still gets in,’’ said Rader, a 30-year veteran of Louisiana’s correctional system.

He added, ‘‘We do shakedowns continuously and we still find stuff, although not as much as some systems find.’’

Corrupt staff provide one avenue for drugs, cell phones and other contraband. Better pay for guards helped cut that problem by attracting better candidates who were less prone to corruption and improving retention rates, Cain said.

‘‘What hurt us was when the pay was so low that we’d hire anybody who could walk and chew gum at the same time,’’ Cain said. ‘‘Most of this is gone now.’’

Travis, chief of operations, said inmates will seek to turn a corrections officer by paying him to bring in small items, such as a pack of gum or a McDonald’s hamburger. An officer who falls into that trap can be blackmailed later into bringing in drugs or other contraband, Travis said.

Rader said the small amount of drugs and contraband that gets into Louisiana’s prisons appears to come in mostly through inmates on outside work details.

‘‘I think less comes in through visitation and more comes in through offenders or employees smuggling it in,’’ Rader said.

The front gate security at a prison is set up to make it difficult for visitors to slip drugs to an inmate. Cars are subject to search and dogs are taken routinely through parking lots to sniff for the presence of drugs.

At Angola, a maximum-security prison, an arriving visitor enters an enclosure resembling a telephone booth. A fan mounted above blows air down over him. A dog on the other side of the wall scratches a screen if it smells drugs.

Corrections officials say drugs and other contraband in prisons often fuel inmate violence as they fight for control of the illicit market.

‘‘It parallels what you see on the streets if you don’t stay on top of it,’’ Travis said.

The consequences at Angola can be severe for an inmate caught with drugs or committing an act of violence against another prisoner.

Most of Angola’s 5,200 inmates live in dorms, work in the fields or at other prison jobs and have limited freedom within the prison grounds.

Inmates who don’t follow the prison’s rules can be sent to cell blocks. The most dangerous and disruptive inmates go to Camp J, where they stay locked in cells 23 hours a day, Cain said.

He said inmates regularly tip him off to the presence of drugs or knives because they don’t want drugs or the violence that accompanies the drug trade inside the prison.

The system appears to work. Few drugs are getting into Angola, and inmate-oninmate violence stays at low levels, according to corrections department data.

Prison data indicates that assaults between inmates caused 13 singificant injuries — those requiring urgent and immediate treatment and which restricts an inmate’s usual activities for six weeks or more, Travis said.

‘‘The federal intervention was critical,’’ said Ross Maggio, warden at Angola in the mid-1970s. ‘‘If it hadn’t been for federal intervention, my hands would have been tied.’’

Once federal authorities took over, the state had to make money available to hire more correctional officers and to pay for other measures to stop the drug trafficking and rampant violence, said Maggio. He later became a court-appointed expert and helped shepherd through many of the reforms still in place at Angola and other Louisiana prisons.

Maggio said building and opening Camp J and other cell blocks to lock away inmates who are disciplinary problems was a critical step in turning around Angola and getting the prison back under the control of administrators.

‘‘Angola has been called the safest maximum-security prison in the country, and I think that’s with a lot of justification,’’ Maggio said. ‘‘It’s come a long way.’’