Two American women were hospitalized in Moscow for treatment of thallium poisoning, the Interfax news agency cited the Russian consumer watchdog agency Rospotrebnadzor as saying Tuesday.
The women a mother and daughter became ill Feb. 24 and were being treated at Moscow's Sklifosovsky clinic, the city's top emergency medicine hospital.
Russian media reports said the women, identified as Maria Kovalensky and her daughter Yana, had come to Moscow for a relative's wedding and were staying in a Moscow hotel when they became ill.
Rospotrebnadzor's Moscow office reported that the women were in "moderately serious" condition, Interfax said. Rospotrebnadzor declined to comment to The Associated Press. The city health department also declined to comment, referring questions to the U.S. Embassy.
An embassy spokeswoman, speaking on the usual condition of not being further identified, said "consular officials are in close contact with the family and we are assisting them," but she did not provide further details, reports AP.
Thallium, often called "the poison of choice," is colorless, odorless and deadly in doses as small as one gram (0.04 ounces). Thallium was initially suspected to be the toxin used in last year's fatal poisoning in London of former Russian security agent Alexander Litvinenko, but it was later determined he had ingested the rare radioactive isotope polonium-210.