(CNN) -- Preliminary results from a U.S. military laboratory show that remains exhumed outside the Russian city of Yekaterinburg in 2007 belong to two children of Russia's last czar, Nicholas II, a spokeswoman for Yekaterinburg regional governor Eduard Rossel said Wednesday.
The results suggest the remains belong to Nicholas' children, Alexei -- who was the heir to the throne -- and Maria, who have been missing since the royal Romanov family was executed in 1918 by Bolsheviks in the basement of a Yekaterinburg home. Several of their staff and servants also were killed.
Nicholas' reign had ended when he abdicated the throne in 1917 at the time of the Russian Revolution.
Natalia Ponomaryova, the regional governor spokeswoman, told CNN that Rossel made the announcement about the identification of the remains of Alexei and Maria at a news conference, where he said, "Now we have found the entire family."
She said the governor learned the information about two weeks ago from an investigator for the General Prosecutor's Office, Vladimir Solovyov. Solovyov, who probed the case for months, shuttled between Moscow to Yekaterinburg to collect information. Yekaterinburg is about 900 miles east of Moscow.
The preliminary results are from the fourth and last set of DNA tests of the czar's family remains. The final results are to be released in late May, the governor's office said.
An archaeologist said last year that clues left by one of the family's assassins led investigators to the makeshift grave where the remains of Alexei, 13, and his sister, about 19, were found.
The remains of the rest of the family were discovered in 1991, during the last days of the Soviet Union. In 1998, those remains -- of Nicholas, his wife, Alexandra, and three daughters -- were interred in a cathedral in St. Petersburg that contains the crypts of other Russian royalty.
The drama surrounding the Romanovs has been the subject of many books, movies and documentaries.
Several women have claimed they were Anastasia, Nicholas' youngest daughter, contending they escaped the execution, but none was proved to be the grand duchess.
The body of one imposter, Anna Anderson, was cremated when she died in 1984. DNA tests showed she was no relation to the Romanov family. E-mail to a friend