Four months after a “bad batch” of drugs caused nearly three dozen people to overdose in West Baltimore, authorities carried out pre-dawn raids and made arrests in the city Wednesday as part of a continuing investigation, sources familiar with the matter said.

It was not immediately clear how many people were arrested and the charges involved. The sources asked not to be identified because they were not authorized to speak publicly about the investigation.

More details were expected to be released in the coming days, according to these sources.

Thirty-five people were treated following the July 10 mass overdose in Penn North, including seven who required ventilators. First responders found people lying unconscious at a bus stop, behind a pharmacy and in the parking lot of a funeral home, among other places.

City leaders credited their quick response along with those from community groups as reasons why no one from the mass overdose died. City agencies coordinated with the state, Baltimore County and 16 community organizations to canvass the area and administer naloxone. Emergency workers and volunteers searched more than 175 vacant buildings looking for possible victims.

Just eight days later, a second incident in the same neighborhood sickened an additional seven people, five of whom went to the hospital. On Oct. 8, 11 more overdoses were reported, with seven hospitalizations.

Police have faced questions from elected leaders and community members about what they are doing to combat continued open-air drug dealing, though others have said a holistic and balanced response is needed.

“This has been a recurring issue that we know we have to address,” Councilman Mark Conway said at a September hearing, demanding a written plan. “We have made significant progress in violence, but we all know, we still have significant complaints and problems that are preventing people from feeling safe in their own homes.”

Police Commissioner Richard Worley told The Banner in August that the overall war on illegal drugs was a failure, saying that mass arrests of drug dealers and users haven’t made the city safer. However, he said, police were still committed to working complex drug investigations that take time.

“We want the supplier who’s bringing the drugs in,” Worley said, adding, “But unfortunately, you have to start at the bottom a little bit and work up.”