"This was dangerous work," Sandweg said.
Some of the firearms seized were homemade, including one gun that resembles a pen, said Angel Melendez, Puerto Rico-based special agent for Homeland Security Investigations of U.S. Immigration and Customs Enforcement.
The operation targeted six municipalities, including the capital of San Juan and the popular tourist town of Fajardo. However, Melendez said the operation was most successful in Ponce, Puerto Rico's second-largest city.
Officials said the drugs seized are mostly cocaine and some heroin imported from Latin America that is being sold locally as well as shipped to the U.S. and Europe. Weapons are being smuggled in from the U.S. mainland through checked luggage, and Transportation Security Administration officials have adjusted screening procedures to catch the firearms, the DHS said.
Agents have increased the number of cargo inspections and strengthened security at the main international airport by adding more dogs and officers with U.S. Customs and Border Protection. The U.S. Coast Guard bolstered its resources in areas including the eastern portion of the U.S. Virgin Islands and the Mona Passage, a popular smuggling route that lies between Puerto Rico and the Dominican Republic.
Nearly 30 agents with Homeland Security Investigations were assigned to the island over the past three months, and an additional seven agents were permanently deployed, DHS officials said.
The three-month offensive focused on street-level enforcement that allowed agents to cull intelligence following the arrests of dozens of suspects, the DHS said.
The island of 3.7 million people is struggling with a crime wave that brought a record 1,117 homicides in 2011.