The World Health Organization has said the risk of an epidemic in Russia is lowafter the sudden death of a lab technician who worked at a plague research institute in Siberia.

Darya Shipilova, who was 28, died last week, two days after falling ill. Russian media reports suggested she may have become infected after an accident at her workplace, where dangerous pathogens are kept and studied.

Russian authorities have downplayed the incident and say Shipilova died of “pneumonia of an unknown aetiology”. Strict quarantine measures have been imposed at the research centre in the city of Irkutsk and in several neighbouring hospitals.

Christian Lindmeier, a WHO spokesperson, said on Tuesday that there was no sign of a wider outbreak. “All ‌of the patients’ contacts have reportedly been identified and are being monitored for ‌illness, and none to date have shown ​symptoms of illness,” he said.

Russian ⁠officials were still ​investigating whether viral pneumonic plague caused Shipilova’s death but the WHO had assessed the health risk as “moderate to low” for Irkutsk, “low” for the rest of Russia and “very low” for Europe, he said.

According to Russian media, 60 of Shipilova’s colleagues have been locked in the institute where she worked since Friday, sleeping on the floors and chairs while tests are carried out. Similar measures have been imposed in five hospitals, with relatives forbidden to see patients.

The Kremlin’s spokesperson, Dmitry Peskov, urged people on Tuesday not to listen to rumours but to rely on statements from Russia’s health watchdog, Rospotrebnadzor. It said the situation in Irkutsk was stable, with no new infectious disease cases reported among institute employees.

Washington has been watching developments closely. The US secretary of state, Marco Rubio, called on Moscow on Tuesday to release more details about the case. “I think it’s incumbent upon ⁠Russia to obviously share more information with ​the world,” he said. “We’re watching it very closely, hour ‌by hour.“

Donald Trump had said earlier that his administration was willing to offer assistance. “I hate to see them having it. We’ll help. Everybody who has that kind of a problem, we’ll always help,” he told reporters at the White House when asked what Washington was going to do about the risk of plague coming from Russia.

In an apparent mirror response, Rospotrebnadzor announced that Russia was prepared to assist the US in combating its own outbreaks of infectious diseases.

“The situation regarding dangerous infectious diseases remains unstable,” it said, highlighting among a “significantly worsened” measles situation in three US states and a “fatal case of plague” recorded in New Mexico in June.