ATR72 CREW HAD NMAC WITH 2 ACFT IN TJSJ CLASS C.

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ON ABOUT A 4 MI FINAL; DSNDING ON THE ILS RWY 10 INTO SAN JUAN; PUERTO RICO (TJSJ); WE HAD 2 TARGETS SUDDENLY APPEAR ON TCASII. THE FIRST TARGET WAS AT OUR 7 O'CLOCK POS; ABOUT 1/2 MI; AND AT OUR ALT. THE SECOND TARGET WAS DIRECTLY BELOW US; 300 FT BELOW OUR ALT. INITIALLY; THE TCASII GAVE A TA OF 'MONITOR VERT SPD;' FOLLOWED IMMEDIATELY BY 'CLB; CLB NOW.' WE INITIATED A CLB; AND PASSING ABOUT 1800 FT MSL; TA OF 'MONITOR VERT SPD' WAS GIVEN AGAIN. I CALLED TWR TO TELL THEM WE WERE CLBING DUE TO AN RA ON TFC DIRECTLY BELOW US. THE CTLR STATED THAT HE DID NOT SEE ANYONE ON RADAR. UNFORTUNATELY; NEITHER TCASII TARGET WAS IN A POS FOR US TO IDENT WHAT TYPE OF ACFT THESE MIGHT HAVE BEEN. HOWEVER; I SUSPECT ONE OR BOTH WAS PROBABLY A HELI. I ALSO DO NOT THINK THIS WAS A TCASII PROB WITH OUR ACFT. IT WAS OUR 3RD FLT THAT DAY IN THE SAME AIRPLANE; AND THE 2ND TIME INTO SAN JUAN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: CAPT RPTED THAT JUST AS HE WAS LNDG THERE WAS A HELI RADIO CALL CHKING IN WITH SJU TWR. THE CAPT ALSO RPTED THIS INCIDENT TO HIS UNION AIR SAFETY PEOPLE. A CONFERENCE CALL WAS ARRANGED WITH SJU TWR QUALITY ASSURANCE. THEY REVIEWED THE RADIO TAPES AND CONCLUDED THAT THE PROB WAS FALSE TCASII OP. NO ATTEMPT WAS MADE TO REVIEW THE RADAR TAPES; SO IT IS UNKNOWN WHETHER THE INTRUDER ACFT WERE DETECTED BY RADAR.