Hundreds more infectious germ samples found at lab near Washington

An investigation into the discovery of six vials of forgotten smallpox at a US government lab has turned up hundreds more samples of infectious biological agents, US regulators said.

"The investigation found 12 boxes containing a total of 327 carefully packaged vials labelled with names of various biological agents such as dengue, influenza, Q fever and rickettsia," said the US Food and Drug Administration (FDA) on Wednesday.

The boxes were discovered in the same cold-storage area of an FDA lab at the National Institutes of Health (NIH) where the six smallpox vials were found.

The smallpox vials dated to the 1950s and were initially announced as having been discovered as preparations for a laboratory move were under way, authorities have said.

"While an investigation continues regarding the origin of these samples, this collection was most likely assembled between 1946 and 1964 when standards for work with and storage of biological specimens were very different from those used today," the FDA said.

"All of the items labelled as infectious agents found in the collection of samples were stored in glass, heat-sealed vials that were well-packed, intact and free of any leakage, and there is no evidence that anyone was exposed to these agents."