DNA tests carried out by a U.S. laboratory prove that remains exhumed last year belong to two children of Czar Nicholas II, putting to rest questions about what happened to Russia's last royal family, a regional governor said Wednesday.

The bone fragments dug up are those of Crown Prince Alexei and his sister, Maria, whose remains had been missing since the family was murdered in 1918 as Russia descended into civil war, said Eduard Rossel, governor of the Sverdlovsk region.

"We have now found the entire family," he told reporters in Yekaterinburg, the city where the remains were exhumed about 900 miles east of Moscow.