Peru's defense minister announced Wednesday an investigation into allegations of military corruption in the world's No. 1 cocaine-producing valley after The Associated Press reported that the armed forces turned a blind eye to the ferrying of cocaine abroad by small planes.

The official, Jakke Valakivi, said the defense ministry and the joint armed forces command would investigate together.

Peru's armed forces have failed to effectively impede an "air bridge" that has delivered more than a ton of cocaine a day to Bolivia in flights that stepped up in tempo in the past few years, according to prosecutors, drug police, former military officers and current and former U.S. drug agents.

In part because of the nearly unhindered "air bridge" from the Apurimac, Ene and Mantaro river valley, Peru surpassed Colombia in 2012 as the world's No. 1 cocaine exporter.

Police say the airborne flow accounts for roughly half of its production, with each planeload worth at least $7.2 million overseas.

The trafficking got so brazen that congress voted unanimously in August to authorize shooting down the single-engine planes. But the government this year inexplicably scrapped plans to buy the required state-of-the-art radar, a $71 million expenditure it announced last November.

President Ollanta Humala has just eight months left in office — and an approval rating below 15 percent.

The "narco planes" have touched down just minutes by air from military bases in the nearly road-less region known by its Spanish acronym as the VRAEM.

About four times a day, they drop onto dirt airstrips, deliver cash and pick up more than 300 kilograms (660 pounds) of partially refined cocaine, police say.

The AP obtained video of two such transactions taken by drug police who said they were too outgunned by assault rifle-wielding sentinels to intervene.

Wilson Barrantes, a retired army general who has long complained about military drug corruption, said giving the armed forces control of the cocaine-producing valley is "like putting four street dogs to guard a plate of beefsteak."

One accused narco-pilot interviewed by the AP said some local military commanders charge $10,000 per flight to let cocaine commerce go unhindered.

Prior to publication, the AP repeatedly requested interviews with Valakivi, armed forces commander and air force to discuss the issue. None responded.

But at a news conference with other ministers Wednesday after a Cabinet meeting, Valakivi tersely announced the opening of the investigation. Minutes earlier, he called the AP's report "tendentious" and said the military rejects corruption in its ranks.

"Corruption exists, but we are always looking out for it," Deputy Defense Minister Ivan Vega, who runs counterinsurgency efforts in the VRAEM, had previously told the AP.

He said he knew of no military officials under investigation. "If we know of anyone involved, we'll throw the book at them."

The board chairman of the anti-corruption nonprofit group Transparency International, Jose Ugaz, said he hoped AP's investigation would spur debate in the presidential campaign.

Sadly, the Peruvian lawyer said, military drug corruption is an open secret in the country. "It's been going on for some time but unfortunately no one has done anything."

Humala, a former army lieutenant colonel, said on taking office in 2011 that combatting illicit drugs was a priority. His government has destroyed record amounts of coca leaf.

But that's not enough, says Sonia Medina, the public prosecutor for illicit drugs.

Trafficking and related corruption in the police, military, courts and criminal justice system have gone "from bad to worse" on Humala's watch, she said. "What we are doing in counter-narcotics is completely distorted, incoherent and inert."

Most of Peru's cocaine production has merely shifted to the VRAEM region, where there is no eradication.

The Ireland-sized area has been under a state of emergency for nine years owing to the persistence of drug-running Shining Path rebels. They have slain more than 30 police and soldiers during Humala's tenure but are now much reduced, down to about 60 combatants.

The government says destroying coca in the region would cause a bloody backlash by fueling Shining Path recruitment.

Some 6,000 soldiers are stationed at more than 30 bases in the valley, ostensibly to battle "narcoterrorism." By law, counter-narcotics is the job of the fewer than 1,000 narcotics police in Peru. But police rely on the military for airlift and many chafe at joint drug missions with soldiers.

In documents and testimony obtained by the AP, police and anti-drug prosecutors questioned the military's trustworthiness. One recalled asking about clandestine airstrips during a 2013 meeting with military officials and watching them "take out their maps, which showed airstrips here and there. They had never informed us of all this."

There were also suspicions of intelligence leaked to traffickers.

Four anti-drug prosecutors complained about it in a May 2014 letter to their boss that the AP obtained.

Three times they shared information with the military on when and where drug flights would land, they said. In each case, the planes never showed. The fourth time, they kept the information to themselves and acted alone with police.

The pilot was captured, the co-pilot killed in a firefight and 357 kilograms of cocaine and $5,500 in cash seized. The March 2014 operation was the only one in the past two years in which drugs, money, plane and pilot were all taken into custody.

Over that period, more than two dozen suspected drug planes have been "captured." Most were after crash landings. In all but five cases, the pilots escaped.

The pilot who said military commanders charged $10,000 per narco flight for safe passage said that "no plane arrives without at least half a million dollars to pay for the drugs, for the airstrip and to corrupt the authorities."

Like others, he agreed to speak only if given anonymity for fear of his life and the AP could not independently confirm his claim.

Before the narco-flight boom, the military sent people to the valley to be punished for transgressions, said Victor Andres Garcia Belaunde, an opposition congressman.

"But it has, alas, become profitable to be in VRAEM and today there are officers who ask to go."

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Investigative researcher Carlos Neyra in Lima, Peru, contributed to this report.