In 2003 New Scientist magazine reported on the contradictory results produced by a French and a British lab looking for evidence of Yersinia pestis DNA from plague corpses:
Case reopens on black death cause
The case remains far from solved. Until we dig up some more corpses.....

"If I can get some soft tissue from the plague, I'll look again," he says. In Finland, for example, there may be victims buried in permafrost.