THE ASSOCIATED PRESS Russian authorities are keeping a tight lid on information about last week’s suspicious death of a lab worker in Siberia that has been surrounded by secrecy and claims that it could have been caused by pneumonic plague.

While the case has raised global concerns, Russian state TV and other national state-controlled media have steered clear of the subject. Some state-sponsored news outlets withdrew earlier reports about the case, which has topped independent online news outlets.

Russia’s public health watchdog, Rospotrebnadzor, said Sunday the lab worker was diagnosed with “pneumonia of unknown etiology,” meaning its origin was not known.

In its official, tersely worded statements, it does not link the case to pneumonic plague, saying only that “extensive” testing found no evidence her illness was caused by any of the pathogens she worked with at the Irkutsk Anti-Plague Research Institute of Siberia and the Far East.

A state TV station in Irkutsk reported she died Oct. 2 in a hospital in Shelekhov, a town just outside Irkutsk.

Officials have quarantined a hospital and are monitoring the contacts of the worker, who died of what unconfirmed media reports said could have been pneumonic plague — a less common but severe form of plague that can spread from person to person.

Moscow informed the World Health Organization that no case of plague has beened in the Irkutsk region in southeastern Siberia.

President Donald Trump said Tuesday he would speak about the issue “very soon” with Russian President Vladimir Putin and report about it “probably tomorrow.”Wednesday is the Kremlin leader’s 74th birthday.

Kremlin spokesman Dmitry Peskov said Wednesday that a Putin-Trump call hasn’t been set yet but could be organized quickly.

Trump said the U.S. stands ready to help Russia. Asked what the U.S. intelligence community was saying about the case, Trump said the U.S. is in “very deep discussions” on the topic.

In response to the WHO’s request to clarify the situation in view of media reports alleging pneumonic plague as the cause of the lab worker’s death, Russia has declared that no case of plague had recently beened in Irkutsk oblast, the U.N. organization said. Russian health authorities reported a full range of preventive measures had been carried out — including tracing of the dead woman’s contacts, medical monitoring and lab tests, WHO said Wednesday.

The Russian note relayed to The Associated Press by the WHO said the test showed “no presence of dangerous infectious disease pathogens in any of the contacts.”The Geneva-based organization said it has requested further information to clarify the cause of the severe pneumonia, the pathogen that prompted the public health measures, and media reports of a second employee with pneumonia of undetermined cause.

The organization said it has remained in contact with Russian health authorities and offered technical support.

Peskov has referred all questions to Rospotrebnadzor, which does not mention suspected plague in its reports.

In its latest statement Tuesday, the agency said “the sanitary and epidemiological situation in the Irkutsk region, the cities of Irkutsk and Shelekhov is calm.”It said authorities were completing a “complex of prophylactic measures and medical observation over contacts,” adding that so far they have found two cases of COVID-19 and two cases of rhinovirus. “No other infectious pathogens have been found among contacts,” it said.

The news outlet Lyudi Baikala — or “People of Baikal” — identified the dead lab worker as 28-year-old Darya Shipilova and said she first was hospitalized with cold symptoms Sept. 29 and died three days later.

It quoted her colleagues as saying she was a highly qualified and diligent researcher. They also emphasized that security rules at the facility, established in the 1920s to monitor and study the plague that is endemic to southeastern Siberia, are extremely strict.

The report quoted Shipilova’s neighbors as saying a team of disinfection experts did several cleanups of her apartment, leaving a strong antiseptic smell.

The hospital where she died was under quarantine, no longer admitting or discharging patients, although its outpatient clinic has continued operating, according to Mayor Maxim Modin.

Irkutsk Gov. Igor Kobzev said she died of a “particularly dangerous infection” and everyone who came into contact with her has remained under medical supervision.

The incubation period for pneumonic plague — the disease’s most virulent form — can be as short as 24 hours, according to the WHO. The lung-based illness is a less common but severe form of plague that can spread between people via respiratory particles. If untreated, the illness can be fatal, but recovery rates are high if detected and treated in time, it said.