The five NFL road teams whose medical staffs were interviewed and subjected to spot checks of their bags by federal agents may turn out to be just the first five in line.

Drug Enforcement Administration spokesman Rusty Payne said that teams were chosen for inspection simply because they were playing away from home. They were the San Francisco 49ers, Tampa Bay Bucs, Cincinnati Bengals, Seattle Seahawks and Detroit Lions. No arrests were made and the DEA declined to comment whether any potential violations of the federal controlled substances act — the stated reason for the inspections — were discovered.

But Payne also noted Sunday that investigators from the agency "are currently interviewing NFL team doctors in several locations," suggesting the federal probe begun this summer into possible drug prescription abuse in the league could involve all 32 teams. Although the NFL said in a statement "we have no information to indicate that irregularities were found," and the Tampa Bay Bucs breezily characterized the spot-check as a "5-minute delay" on Twitter, at least one former federal prosecutor called the inspections "a big step forward."

"When someone from the government — even without a warrant — walks up and asks questions, they get answers and you can test those answers," said Steven Feldman, a former assistant U.S. Attorney for New York's southern district with considerable experience in narcotics prosecutions.

"They're either going to tell the truth or lie, and you can use either one in an investigation. Having worked with DEA investigators in the past, it's just one more step. My guess," he added, "is that this one is a long way from being complete."

In response to questions Monday from Associated Press reporters, nine teams said no one in their organization, including medical staff, had been contacted by investigators from the DEA.

Here's several things to know as the investigation going forward:

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WHY DID THE DEA GO PUBLIC WITH THE INVESTIGATION NOW?

The probe was sparked by a lawsuit filed in May on behalf of 500 former players who claimed they were routinely — and often illegally — given powerful narcotics and other drugs such as Vicodin and Oxycontin to mask pain and keep them on the playing field. Over the last several weeks, investigators criss-crossed the country to interview at least a half-dozen former players — including at least two who were named plaintiffs in the painkillers lawsuit, according to multiple people with direct knowledge of the meetings who spoke on the condition of anonymity because prosecutors told them not to comment on the meetings.

"To me," said Feldman, "the timing suggests they're looking for someone who can provide a narrative of what went on inside the locker rooms. They have some of that from the players ...but to expand it, they need someone on the other side. Someone who can be squeezed, who acknowledged giving out pills, or who can say whether it was a policy higher up the organization. ... So team doctors and trainers are certainly one place to go looking."

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WHAT WERE DEA INVESTIGATORS LOOKING FOR?

The federal controlled substances act stipulates that only doctors and nurse practitioners can dispense prescription drugs, and only in states where they are licensed. The act also lays out stringent requirements for acquiring, record-keeping, labeling, storing and transporting drugs. Trainers who are not licensed would be in violation of the law simply by carrying a controlled substance.

The lawsuit contends some teams filled out prescriptions in players' names without their knowledge or consent, and that trainers often dispensed those drugs "like candy at Halloween," along with combining them in "cocktails."

But proper documentation for any controlled substances found in possession of the medical staff may not have been the sole reason for the inspections.

Agents occasionally leak information about an inspection or raid to set up with what's known as a "time-date stamp," and later subpoena any electronic communication between parties that are under investigation, a practice Feldman is familiar with.

"We' called it 'tickling the wire' when I was a prosecutor," Feldman said, "because at the time, email wasn't as prevalent and we went after the communications between parties with wiretaps. So it sounds quite plausible in this case."

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DID ANY OF THE TEAMS OBJECT TO THE INSPECTIONS OF THEIR MEDICAL STAFFS?

Most barely noticed.

"Right after a big game like that, there's a lot of sleeping going on" Tampa Bay coach Lovie Smith said Monday. "So I caught most of it. I don't know, a few minutes. Fifteen minutes or so. I don't really know how long."

San Francisco coach Jim Harbaugh said he didn't hear from or even see the DEA officials, only learning there was an inspection of his team's staff when he "read about it." But he didn't sound worried either way.

"We're an open book in those regards," Harbaugh said. "Any kind of scrutiny, any kind of questions, we're an open book there."

The most interesting response may have come from the Cincinnati Bengals, who were spot-checked in New Orleans. After agent Debbie Weber, a spokeswoman for the DEA's New Orleans office pronounced the team was in compliance, the team added in a statement: "The Bengals have never had any issues regarding prescriptions/controlled substances."

"Any issues which might be present elsewhere are not present with our organization," the statement said.