An Amber alert is in effect in Massachusetts for 4 children who were apparently taken from an apartment where police investigators found another woman who was stabbed to death.

The children, aged between 11 months and 3 years, are believed to be with their father, Rodlyn Petitbois. Police are seeking an arrest warrant for the father on a first-degree murder charge.

"At this point in time we believe Rodlyn is extremely dangerous and may be armed," Essex District Attorney Jonathan Blodgett said.

Lynn police went to the apartment after receiving a report about a stabbing early Wednesday that had taken place there. Police officers found a 33-year-old identified as Greenland Etienne with stab wounds to her face. The stabbed woman was taken to Massachusetts General Hospital where she was pronounced dead after a few hours.

According to police investigators, all clues seem to lead to the conclusion that there was a "social" relationship between the missing family and Etienne, but what kind of link was it is still under investigation.

Blodgett said that the mother of the 4 children, Louna Eveillard, may be wearing a bandage on one of her hands. The District Attorney added that he received a report according to which a family was sighted in Boston's Haymarket Square. The family may be traveling by bus.

The 4 missing children are: Ryan Petitbois, 3; Lyndsey Petitbois, 2; Lauren Petitbois, 22 months; and Roddick Petitbois, 11 months. Their parents came to the US from Haiti in 1999 through New York. NYC authorities have been put on notice.