Russia says it

Russia's government said Wednesday that it was open to "promptly" scheduling a phone call between Presidents Trump and Vladimir Putin to discuss the still-unexplained death of a plague research center employee, but that nothing had been scheduled yet.

A State Department spokesperson later told CBS News the U.S. Embassy in Moscow had "engaged Russian authorities about the reported death" and "asked for additional information," which it encouraged Russia to share "quickly and transparently."

The United Nations World Health Organization called Wednesday on Russia's national health watchdog agency, Rospotrebnadzor, to provide more information about Shipilova's death, and the Russian body said it had provided further details.

The agency said it had conducted nearly 5,000 lab tests of those individuals and that none of them had detected dangerous pathogens.

Rospotrebnadzor's statement added that Shipilova had been vaccinated against the dangerous infections she worked with, so she had immunity to them.

According to its website, the Irkutsk anti-plague lab's work extends beyond research on the well-known bacteria, which is present in animal populations in the region, as it is in other parts of the world, to include planning and preparation on how to deal with incidents involving "potential agents of bioterrorism."

Irkutsk lab was previously a "cover for a biological weapons facility"

When it comes to "the accidental release of a genetically modified pathogen from a high or maximum containment laboratory around the world," she told CBS News, "the number-one worry is Russia."

She told CBS News all the scrutiny Russia has drawn this week is due not only to the reports by independent media of Shipiova dying of a possible plague infection, but also to"the quarantine of some 200 people" under what she said were "draconian measures."

The WHO said Wednesday that it had requested more information after some media reports suggested a possible second infection in the area, but nothing has been confirmed so far.

Lyudi Baikala, an independent Russian news outlet that was among the first to break the news of Shipilova's death, and to say it could have been a plague infection, quoted a colleague of Shipilova's on Tuesday as saying her illness began with cold symptoms before worsening rapidly.

After she was hospitalized, about 200 colleagues were reportedly quarantined at the research institute for three days, and tested twice daily before being released.