The suspect in the chilling death of a young woman whose body was found bound and stuffed in a suitcase and left on the side of a road in an upscale Connecticut suburb was in the country illegally, according to law enforcement sources.

An ex-boyfriend has been arrested in connection with the death of Valerie Reyes, whose body was found bound in a suitcase on a street in an upscale Connecticut suburb last week, police and Reyes’ mother said.

The suspect in a series of knifepoint robberies at more than two dozen businesses in Queens and on Long Island in a spree that attracted the attention of the FBI was charged with a federal crime on Thursday — a day after he was taken into custody in a Long Island parking lot following a pair of botched heists, police said.

Police are still searching for the man who allegedly stabbed his girlfriend and all three of her children Wednesday morning, killing the woman, his daughter and one of her other children at a hotel being used for homeless housing, authorities said.