Six men pleaded guilty Monday to federal charges connected to a large-scale investigation into the trafficking of heroin and cocaine from the Dominican Republic and Puerto Rico into southeastern Connecticut.

The group, which included men from New London, Groton and Niantic, entered guilty pleas to drug-related offenses in federal court in New Haven, according to a statement from U.S. Attorney Deirdre M. Daly.

The men were arrested in April as part of an investigation led by Homeland Security Investigations and the New London Police Department that ultimately led to more than 100 arrests on a variety of state and federal charges. Numerous state and federal law enforcement agencies were involved with the investigation.

At the center of the investigation was Luis Ariel Capellan Maldonado, also known as “Ariel,” who from his apartment building on Hawthorne Drive in New London supplied customers with raw heroin and sometimes supplied cocaine to wholesale cocaine distributors in New London, authorities said. Police said he regularly procured large shipments of heroin from the Dominican Republic and obtained heroin from other sources in New York City and Rhode Island.

Capellan Maldonado, 27, a citizen of the Dominican Republic, pleaded guilty to federal charges in November and awaits sentencing. On Monday, the following six individuals pleaded guilty to heroin conspiracy charges:

Miguel Morales, also known as “Neow,” 49, of New London; Jose Morales, 53, of New London; Lester Fantauzzi, 47, of Niantic; Emmanuel Blanco Balbuena, 29, of New London; Jose Reynoso-Monegro, 44, of New York, N.Y.; and Edwin Cepeda, 34, of Groton.

The men face a range of charges carrying maximum penalties ranging from 20 to 40 years in prison when they are sentenced in April.

The federal case is being prosecuted by Assistant U.S. Attorneys Alina P. Reynolds, Sarah P. Karwan and Henry K. Kopel. The state cases are being prosecuted by the New London County State’s Attorney Michael Regan with Senior Assistant State’s Attorneys Paul Narducci and Stephen Carney.