The Syrian government, almost a week after a chemical weapons attack killed more than 300 people, is finally allowing United Nations inspectors to visit the site.

The team is scheduled to arrive some time Monday although U.K. Foreign Secretary William Teague says evidence could have been tampered with, degraded or even destroyed in the days since the Wednesday attack.

The Syrian government blamed the attack on “terrorists” despite multiple videos from the rebels showing the victims of the attack. State media claims that chemical agents were found in tunnels used by rebel fighters.

Russia, Syria’s biggest ally, has said the “west” needs to not “pre-empt” the results.

Doctors Without Borders stated Saturday that three Damascus area hospitals treated around 3,600 patients with “neurotoxic” symptoms. The report says 355 of those patients died.

DWB said they could not “scientifically confirm” chemical weapons but that hospital reported a “large number” of patients with convulsions, pinpoint pupils and breathing problems.

A spokesman for U.K. Prime Minister David Cameron said that “this crime must not be swept under the carpet.”