Los Angeles ? Two American women who were hospitalized in Moscow for suspected thallium poisoning flew home to the United States on Wednesday, as colleagues and relatives tried to understand how the two were exposed to the potentially fatal chemical.

Dr. Marina Kovalevsky, 49, and her daughter, Yana, 26, arrived at Los Angeles International Airport and were taken in wheelchairs past news media to two waiting ambulances and placed on gurneys.

A cousin said earlier the women would be going to Cedars-Sinai Medical Center.

In Moscow, a U.S. Embassy spokesman said Russian officials were investigating how and when the women could have come into contact with poison.

Moscow police declined to comment, but the Ekho Moskvy radio reported authorities were checking cafes and restaurants in the area of the hotel where the women stayed. The women are Soviet-born and immigrated to the United States in 1989. They have visited Russia repeatedly since then, relatives and colleagues said.