ZSU controller described near separation event when departures from SIG and SJU were released simultaneously; reporter alleging multiple runway closures and time frames were a contributing factor.

Narrative

SIG is Municipal Airport and SJU is an International Airport. These 2 Airports are relatively close to one another and when you clear an aircraft to SJU to RWY 10 you must not release an aircraft out of SIG because SIG's RWY 9 is aprox. 2.5 miles north from the final approach course of RWY 10 at SJU Airport. Lately SJU has been closing RWY 10 and Rwy 8 on different occasions and not during the same time; of course. SJU called me and told me that RWY 8 was closed and somehow I thought; or understand; that RWY 10 was closed. And I still cleared an ATR from the south of the field for RWY 10 to SJU and release an aircraft out of SIG on a left turn heading 300. I called SJU to reverify if it was RWY 10 that was closed and to switch the ATR to Rwy 8 but they indicated the contrary. The position of the ATR was south of SJU and turned base pretty close to SJU not getting near SIG's departure. I never lost the spacing but this makes me realize that in the morning I need to be even more alert and if in doubt reverify before taking any action.