President Donald Trump said Tuesday that he has scheduled a call with Russian President Vladimir Putin to discuss the death of a laboratory worker at an anti-plague research institute in Siberia's Irkutsk region, according to remarks made to reporters at the White House.

Trump told reporters the call would take place "very soon" and that the United States is in "very deep discussions" on the matter. When asked what U.S. intelligence agencies were saying about the situation, Trump said more information could be reported "probably tomorrow." The Kremlin did not immediately respond to requests for comment on Trump's remarks.

The incident centers on the death of a 28-year-old laboratory technician at the Anti-Plague Institute of Siberia and the Far East in Irkutsk. Russian health authorities identified the woman as Darya Shipilova and said she died from pneumonia of undetermined cause. Some local media reports suggested she may have contracted pneumonic plague following a laboratory accident—either from a broken test tube containing the pathogen or during a field trip to an area where plague naturally occurs in wild rodents. Russian officials have downplayed these reports, and postmortem tests conducted by authorities have not confirmed plague.

Russian health watchdog Rospotrebnadzor said in an official statement that no microorganisms linked to the woman's professional work were found in her biological samples and that no other staff at the institute had sought medical attention since her death. The agency announced that around 200 people who came into contact with Shipilova were placed under medical observation, though approximately 60 percent of those quarantined were later released. Testing of those contacts found two cases of COVID-19 and two cases of rhinovirus, but no cases of plague.

U.S. officials have expressed concern about the incident. Secretary of State Marco Rubio said Tuesday that the U.S. had been monitoring the situation "very closely, hour by hour" and called on Russia to share more information with the world. "I think it's incumbent upon Russia to obviously share more information with the world," Rubio said during a news conference in Iceland. "Maybe, you know, there's nothing there. Maybe it's bigger than we thought. We don't know." A State Department official confirmed that the U.S. had been in contact with the Russian government about the incident since as early as Friday, when Shipilova's death was first reported.

The World Health Organization issued a similar call for transparency on Tuesday. WHO Director-General Tedros Adhanom Ghebreyesus stated that "timely, complete and transparent information sharing under the International Health Regulations is essential to clarify conflicting reports and enable an accurate assessment of potential public health risks." However, the WHO also assessed that the risk of pneumonic plague spreading outside Russia is "very low," with WHO spokesman Christian Lindmeier saying there was no indication the situation resembled a pandemic-level concern. According to the WHO, pneumonic plague has a very short incubation period—sometimes as little as 24 hours—and is highly contagious through respiratory droplets. Without early diagnosis and treatment, the disease can be fatal.

Trump previously stated on Monday that the United States would be willing to offer assistance to Russia if needed. "I hate to see them having it," Trump told reporters. "It's a rough disease. You know, that's a disease we used to be able to control, but somehow those microbes have gotten stronger and smarter. They're like an army. Anybody that has that kind of a problem, we're always willing to help." In apparent response, Russia's health watchdog said Tuesday that Moscow was prepared to assist the United States in combating its own outbreaks of infectious diseases, pointing to measles cases that have increased in three U.S. states and a fatal plague case recorded in New Mexico in June.

The U.S. Embassy in Moscow issued a health alert Tuesday urging Americans in the Irkutsk region to follow guidance from local health authorities, avoid affected facilities, and seek medical care promptly if they develop fever or respiratory symptoms. The Centers for Disease Control and Prevention said it was aware of and monitoring reports of the suspected pneumonic plague case and that "at this time, there is no indication of a broader threat to the United States."