12:35 PM PT -- Police caught a suspect on the grounds, and determined he'd actually forced his way into the residence. Farmington PD says Elwin Joyce has been charged with 2nd degree burglary, trespassing, criminal mischief and attempted larceny.

Police say Fiddy's security was alerted when an entry alarm went off, and then called cops.

50 Cent's Connecticut estate is surrounded by police right now as they investigate an attempted break-in ... TMZ has learned.

Several marked and unmarked police vehicles were in the driveway and on the street Tuesday afternoon outside the Farmington, CT spread. Sources connected to Fiddy tell us police were alerted by someone on the property.

It's unclear if anything was taken ... or if anyone's been arrested. We're told 50 Cent was not home at the time.

One possible reason for so many cops responding -- the place covers a ton of ground ... 50,000 sq. feet for the home on 17 acres of land.