Inspectors from the Organization for the Prohibition of Chemical Weapons (OPCW) on Saturday arrived in the Syrian town of Douma, where an alleged chemical attack took place earlier this month, the Russian foreign ministry said, according to AFP.
The inspectors had been in Syria for a week but had not travelled to Douma because of security fears.
"According to the information we have, the special OPCW mission... arrived on the morning of April 21 in the city of Douma at the sites suspected of having toxic substances," the ministry said in a statement.
"The security of the OPCW has been guaranteed not only by the Syrian side but also by the Russian command in Syria."
Western powers say the April 7 attack involved chlorine and sarin and killed dozens and have blamed the regime of Bashar Al-Assad for the attack.
Their mission was put on hold after a United Nations security assessment team were fired at, and officials at the OPCW have said that Russian and Syrian forces have likely removed key evidence.
The U.S. said Thursday it has "credible information and intelligence" that shows Russian and Syrian regime officials are sanitizing the site of the attack.
The Syrian government has consistently denied using chemical arms and invited the OPCW to investigate.
The Russian ministry said it expects the OPCW to carry out an "impartial investigation", according to AFP.
"Especially since this is the first visit to the scene of a suspected chemical incident in the history of the so-called Syrian chemical record," it said.
Russia, which is a close ally of the Syrian regime, has accused Britain of staging the Douma attack.
Moscow also vetoed a U.S.-drafted Security Council resolution that would have set up an investigation into chemical weapons use in Syria following the Douma attack.