Editor's note: This story was updated Wednesday to include a response from the DEA received late Tuesday.

FAIRBANKS — A Fairbanks father and son who allegedly distributed methamphetamine to lower-level dealers are behind bars after they were arrested recently during the delivery of more than a pound and a half of meth, according to charging documents.

Warren Eugene McDaniel, 57, and Gene Brandon McDaniel, 32, both face federal charges of distributing methamphetamine and conspiring to distribute methamphetamine. Their alleged accomplice, Matthew Alan Burris, 28, was charged with attempted possession of methamphetamine with the intent to distribute for his role in accepting a drug shipment in downtown Fairbanks last Thursday.

The investigation leading to the arrests involved an informant working for the Drug Enforcement Administration, who was accidentally outed to the suspects when a law enforcement officer inadvertently left confidential DEA documents at the younger McDaniel’s apartment.

According to sworn statements by the DEA, which were attached to criminal complaints filed against the men in federal court Tuesday, this is what happened:

A person arrested in February 2013 in Fairbanks with four ounces of meth and $67,000 in drug proceeds admitted having collected money from six or seven local dealers to purchase drugs from a connection in Arizona. The person — identified in the complaints as “CS” for “confidential source” — said the McDaniels had taken over the distribution operation using the same Arizona connection, who would send the drugs to Fairbanks via the United Parcel Service.

The confidential source, who was put on the DEA’s payroll and has not been charged, reconnected with the McDaniels and the Arizona source and agreed to allow the DEA to record phone conversations with the men.

In one deal, the confidential source bought a half-ounce of meth from the McDaniels in May 2014. The recorded phone calls indicated the drugs were part of a larger shipment from Arizona. Investigators seized the half-ounce shipment and deposited $700 in Warren McDaniel’s bank account.

In late September, the confidential source learned about a shipment worth $9,000 on its way to the McDaniels in Fairbanks. The elder McDaniel told the confidential source the shipment was being sent to a Second Avenue address.

On Thursday, investigators in Anchorage at the UPS sorting facility found a package sent from Arizona and addressed in sloppy handwriting to the Second Avenue location in Fairbanks.

“The parcel was heavily taped over every seam, which based on my training and experience is commonly done to mask and seal the contents from being detected by a (drug dog),” the charges state.

But a dog did detect the drugs, and after investigators got a search warrant, they found 774 grams of suspected meth inside the package. That is about 27 1/2 ounces, a little less than 1 3/4 pounds. It was packed in five heat-sealed bags, covered in plain wrapping paper and hidden inside a large blanket.

The investigators replaced the meth with fake drugs and put electronic devices in the package to track it and alert them when it was opened. Then they sent it on its way to Second Avenue in Fairbanks.

That afternoon, the investigators watched as a man later identified as Burris arrived to pick up the package. He then allegedly drove to an address on Picket Place, and the younger McDaniel, who lives in an apartment across the street, showed up to get the package.

A short time later, when the McDaniel son was arrested, the investigators found some of the packaging in his pickup. He had apparently ditched the sham drugs and the blanket covering them near some trees adjacent to the parking lot for his apartment building. Inside the apartment, they found materials to package the meth for local distribution, as well as digital scales and UPS receipts. The investigators also found a scale in Burris’ car.

Warren McDaniel, the father, confronted the investigators while they searched his son’s home.

“During a search of his son’s residence, a copy of a confidential law enforcement operations plan was mistakenly left at the scene,” the charges state.

The elder McDaniel found the document, which detailed the meth-trafficking conspiracy, including the confidential source’s cooperation with law enforcement.

“Warren Eugene McDaniel became understandingly angry and called the CS and told him that he had a document that says that the CS was an informant involved in his son’s arrest,” the charges state.

McDaniel followed up by texting a page of the plan that revealed what law enforcement knew about the alleged conspiracy.

Court records show the McDaniels and Burris were arrested Saturday.

Jodie Underwood, a Seattle-based DEA spokeswoman contacted Tuesday by the News-Miner, said she could not discuss the case because it involved a continuing investigation and internal review.

Underwood did not answer questions about how the operations plan ended up in McDaniel’s hands or whether steps had been taken to protect the confidential source.

"The safety and wellbeing of those assisting in our investigations is of the upmost priority, and we take precautions to protect their identities," Underwood wrote in an email.

Both McDaniels men and Burris appeared in court in Fairbanks on Tuesday. If a grand jury indicts them, they will enter their initial pleas at that time.

Because the case was ongoing, the federal prosecutor on the case, James Barkeley, said he could not comment on the alleged evidence in the charging documents, including the operations plan mistakenly left at the search scene.

But when asked if 774 grams of meth was, generally speaking, a large amount for Fairbanks, Barkeley said yes.

“Anything over a pound is a significant amount of methamphetamine,” Barkeley said. “That’s a lot for anywhere.”

Staff writer Casey Grove is the News-Miner’s Anchorage reporter. Contact him at 770-0722 or follow on Twitter: @kcgrove.