An anonymous tipster reached out to NPR a few months ago with an intriguing allegation: A high-ranking elected official in Chicago took out a suspicious pandemic loan back in 2021.

To start this story at the end: The tip didn't pan out. We never found any reason to believe the official received one of the forgivable loans in the Paycheck Protection Program, or PPP, meant to keep businesses afloat and preserve jobs during the pandemic.

But the fact that it took us weeks to reach that conclusion illustrates the hazards in the current hunt for pandemic fraud in the aftermath of the distribution of billions of dollars of federal aid.

That hunt has been driven by a very public — but incomplete — database of PPP loan data, posted by the U.S. Small Business Administration after it was sued by news organizations. Some outlets have set up websites that make the data easily searchable by the general public.

The PPP data can be filtered for names, addresses, lenders, dollar amounts, and a few other details. It's just enough information to raise suspicions, but not enough to prove them.

Common names and borrowed addresses

Those suspicions have run rampant in Chicago, a city with a history of corruption scandals and sharp-elbowed politics. Rumors of misdeeds, inferred from the PPP list, spread quickly.

The problem with this list is, it's often hard to verify identities, especially in cases of common names. Addresses are not enough to go on, because many loans appear to have been taken out using borrowed street numbers.

This is less of a problem for law enforcement and other investigators, such as the inspectors general in our All Things Considered story about PPP investigations in Chicago, because they can subpoena supplemental data. For instance, the OIG of Chicago Public Schools describes in a report released today how it used bank records to confirm that school administrators took out PPP loans.

But there aren't nearly enough official investigators to look into the more than $200 billion worth of pandemic business loans that have been deemed potentially suspect, nationwide.

That leaves journalists — and members of the public, such as our anonymous tipster — to comb through the public loan data, looking for suspicious patterns.

Some of those patterns can be compelling — such as the fifty applications for small business loans that listed the same address: a day shelter in Chicago where the homeless or other people can pick up their mail, as we recount in our story.

Other intriguing patterns take a little more data-crunching to identify. Nick McMillan, of NPR's Investigations Team, did an analysis of recurring names linked to recurring addresses. The most "frequent" name on Chicago loans was Michael Williams — there are 29 of them — and 14 of those Michael Williams gave addresses which, in turn, were used for other PPP loans under different names.

Experts say those recycled addresses can be a red flag for fraud networks, or loan application assembly lines.

But mixed in with that are innocent people with common names who really did have small, one-person businesses, and were legally entitled to federal aid during the pandemic.

A searchable database that's not going away

One institution trying to untangle these patterns is the Chicago Housing Authority, whose Office of Inspector General ran the public PPP list against its list of people receiving low-income housing benefits. About 8,800 names and addresses were initially flagged; as of last month, about 40 recipients of housing vouchers had been terminated from the program because of PPP fraud allegations, with another 592 now in process of termination.

Approximately 1200 families living in public housing have been identified through what the OIG calls "PPP loan analysis," but the outcomes of those cases haven't yet been reported.

These wide-net investigations worry Dennericka Brooks, who runs the housing law program for Chicago Legal Aid.

"We've seen a lot of identity theft," she says. "We've seen a lot of people who've had their old addresses used to apply for a loan, or [by] someone who has helped them fill out their taxes in the past."

Brooks is wary of the long-term effects of the searchable PPP loan data.

"No one knew that there would be a database that became public, for everyone to be able to look into," she says. "I don't anticipate that many people knew that there would be collateral consequences to accessing this resource."

But the SBA database is public and will remain so. It's led to criminal prosecutions, firings, and it may become a problem for future public officials and politicians.

Which brings us back to the tip. The tipster, digging through that public data, was intrigued by a $20,000 PPP loan for an unnamed catering business, which was taken out by someone sharing the name of the elected official in Chicago. The loan came from a Florida-based lender which processed a similar PPP loan on the same date for someone else — who happened to have a name very similar to that of someone close to the elected official.

That struck our tipster — and, admittedly, us — as quite a coincidence. Add to that the fact that, when we called the phone number associated with the address on the loan, all we ever got was an answering machine that played Marvin Gaye's "What's Going On."

There was nothing left to do but visit the address: an apartment, just north of Chicago's Loop. We rang the unit, but the phone was disconnected. The name on the mailbox was different from the name on the loan.

When a neighbor appeared, she confirmed that someone by that name did occasionally "stay" in the building.

But when asked if was the elected official of the same name, she had to laugh. "It's not [him], trust me!"

As reporters and the public continue to dig through the PPP database, it's important to keep in mind that patterns and coincidences may be intriguing, but they're not the same as proof.