The number of foreclosure deeds filed in Massachusetts fell 65% in May from a year ago,  The Warren Group said Thursday. While the real estate research firm noted declines of more than 60% in both foreclosure deeds — the final stage of the process — and in foreclosure petitions, it is still unclear what impact delayed foreclosures are having on the overall real estate market. “Lenders are continuing to be cautious with the legal process, which is causing a drop off in foreclosure starts and deeds,” said Vincent Valvo, group publisher and editor-in-chief of Banker & Tradesman. In May, Massachusetts reported 454 foreclosure deeds, down from 1,294 a year earlier, and the first time monthly deeds have fallen below 500 this year. In the first five months of 2011, the Bay State recorded 2,566 foreclosure deeds, compared to 6,118 a year ago. Auction announcements on foreclosed homes fell 36% last month to 1,832 from 2,860 in May 2010. Write to Kerri Panchuk.