Janek's service in Jordan - what was spilt?

In Prometheus while Janek is in Vickers' quarters, he mentions serving in Jordan and in particular mentions one building surrounded by barbed wire fencing. He then goes on to mention the barbed wire wasn't to keep them out, it was to keep them in.

"We knew they were makin' something in there and we knew it was bad"

I'm sure you know how the rest of it plays out. 

Does anyone know what they were making?