Two American women were hospitalized for treatment of thallium poisoning, the Interfax news agency said Tuesday, citing the Russian consumer watchdog agency Rospotrebnadzor.
The women became ill Feb. 24 and were being treated at Moscow's Sklifosovsky clinic, the city's top emergency medicine hospital, the report said.
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." She did not provide further details.
Thallium is colorless, odorless and deadly in doses as small as 0.04 ounces. It 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.