I won't be at all surprised to see Israel do something fairly violent about this.
An Israeli television report said on Tuesday that Iran is building a facility in northwest Syria to manufacture long-range rockets, and showed satellite images it said were of the site under construction.
. . .
The Channel 2 television news report showed images it said were taken by an Israeli satellite showing a site in northwest Syria near the Mediterranean coastal town of Baniyas, saying some of the construction indicated explosives would be stored there.
The images from the Eros B satellite showcase the site's ability to store underground missiles, the reports said.
It compared images of buildings it said were of a rocket factory near Tehran to structures at the Syrian site, and said there was a strong resemblance between them.
There's more at the link, including photographs.
There's no way Israel will permit the manufacture or assembly of such missiles in a location where Hezbollah or Hamas terrorists can get their hands on them. It's too great a threat to Israel's security. I've no doubt that warnings have already been dispatched to all concerned, setting a hard deadline for the demolition of the entire site. If those warnings aren't heeded, I daresay Israel will do the demolition itself. That won't please Russia, which sees Syria as a client state, but I suspect they'll understand, and probably won't protest too loudly.