In San Francisco, a development project is being planned on a site that was once home to some of the city’s most famous gay bars. The development could be blocked though, by the discovery of a network of underground tunnels used by bar patrons to escape police raids, SFist reports.

The only catch is that it’s not clear who’s actually seen these secret tunnels.

The development would put a hotel and condos at 950 Market Street, on a block once considered part of the “Meat Rack,” a nightlife district for gay men and trans people. One of the most famous, the Old Crow, survived here from 1935—and perhaps even earlier, as a speakeasy—through the 1980s. In those earlier years, from the 1930s to the 1950s, police would regularly raid and shutter bars associated with gay nightlife.

As the development project nears its final approvals, preservation activist Nate Allbee turned up photos of underground tunnels that connected the bars in this area and would have allowed patrons to escape those raids, SFist reports.

The photos show spacious basements, dusty stairwells and vintage liquor bottles.  So many gay bars faced raids and were shut down in the 1930’s, 40’s, and 50’s, and it’s never been clear how places like the Old Crow managed to stay in business so long. The tunnels may be the answer,” Allbee told SFist.

But another local news outlet, KPIX5, was unable to locate the tunnels. The CBS affiliate reported that Allbee did not take the photos himself and wouldn’t say who provided them. The development group told KPIX5 that “This is the first time we’ve heard that there is a tunnel…As far as we’re concerned, there is no tunnel.”