"This is a professional group we believe from South America," said Lt. Jim Baitinger of Lower Merion Township Police.
LOWER MERION TWP., Pennsylvania (WPVI) -- Police are investigating a string of brazen break-ins on the Main Line.
Lower Merion police say they've had 13 residential burglaries since September. Victims have reported jewelry, cash and electronics stolen.
The most recent one was on Sunday.
Police put out a warning to residents on Wednesday.
"This is a professional group we believe from South America," said Lt. Jim Baitinger of Lower Merion Township Police. "More than one group more than likely. They do not want to encounter people in their homes. They will generally look to see if a home is unoccupied."
Lower Merion police say the people behind these burglaries are organized, waiting for homeowners to leave and mainly striking in the evening.
SEE ALSO: Main Line homes hit by organized burglary ring targeting high-end jewelry
And alarm systems don't seem to be a deterrent.
"They will go around back to try to make a rear entrance. They'll break a window. Break a sliding glass door," said Baitinger.
Police say there's a bit of delay from the time the alarm goes off until police are ultimately called.
Police say it's happened in Villanova, Gladwyne, Bryn Mawr and Penn Valley, and they're asking residents to check any surveillance cameras for anything suspicious.
Last week in Radnor, surveillance cameras caught two men breaking into million-dollar homes, taking expensive handbags and jewelry.
Similar burglaries were also reported in Abington.
"We have video surveillance footage. They're wearing hoods. They have masks. They're wearing gloves. They're wearing bulky clothing," said Baitinger. "The things that we're finding of evidentiary value are not great at this point."
Police here say they have a vacant home program where police will check on your home while you're away if you sign up.
Anyone with information or surveillance footage should contact Lower Merion detectives at 610-645-6228.