Any evidence of chemical weapons used by the Syrian regime may have already been destroyed.

That's the warning tonight from the British Foreign Secretary, William Hague, amid reports that Syrian officials are finally allowing UN inspectors to examine a site in Damascus tomorrow.

They want to investigate whether chemical weapons caused the deaths of more than 300 people.

But Mr Hague is pessimistic about what can be found - five days on.

Meanwhile, residents of the Syrian capital say they are afraid their food and water supplies may be contaminated.

There are claims that the poison gas hit an area where acres of agricultural land supply the capital of three million people with fresh vegetables, meat and dairy.

Syrian authorities have yet to respond with any clarity about whether people need to take special precautions to protect themselves from possible contamination.

It is not yet clear what poison or mixture of poisons were responsible for the killings.