UNITED NEWS INTERNATIONAL (UNI) —The United States has accused Syria and its ally Russia of tampering with evidence of a chemical weapons attack.

Inspectors from the Organization for the Prohibition of Chemical Weapons, or OPCW, traveled to Syria to inspect the site of an alleged chemical weapons attack.

However, they have yet to reach Douma, where the attacks reportedly occurred.

The government allegedly carried out the attack while reclaiming the town from rebel forces, eliciting retaliatory airstrikes over the weekend from the U.S., Britain and France.

A U.S. diplomat accused Russia of trying to thwart the investigation at an OPCW meeting on Monday.

Meanwhile, the United Kingdom accused Russia and the Syrian government of denying access to the OPCW inspectors.

However, Russian Foreign Minister Sergei Lavrov denies a chemical attack took place and said Russia hasn’t tampered with the site.

Russia also blamed the Western airstrikes for slowing down the inspectors.