Police, fire and rescue vehicles line Shawmut Avenue, in New Bedford, where more than a hundred people were made ill by unknown fumes at a city trash plant.

The Providence Journal / Kris Craig

NEW BEDFORD, Mass. –– Exposure to “an unknown substance” at a trash-collection company Monday sent 119 people to area hospitals and left two of them critically injured. The two — believed to be plant workers — were unresponsive and breathing with the aid of ventilators, hospital authorities said. Two others were in fair condition.

Most of the others brought to the hospital were suffering inhalation injuries, and irritation of the mouth, nose and eyes, authorities said.

The incident at ABC Disposal Services Inc., at 1245 Shawmut Ave., triggered a regional “mass casualty incident” response, drawing dozens of emergency vehicles from as far away as Bourne, Westwood and Wrentham. At least 50 people were evacuated by school bus from five surrounding businesses along Shawmut Avenue, near the New Bedford Regional Airport.

A criminal investigation was under way, as a precautionary measure, said police Chief Ron Teachman. He said that though there was “no reason to believe it’s criminal,” the investigation would start there to determine that possibility.

HAZMAT responders in encapsulated suits were combing through trash brought into the facility Monday afternoon to try to identify the substance. Some 60 teams from around the state were rotating the job because their suits made them vulnerable to the oppressive heat, said state Fire Marshal Stephen D. Coan.

Coan said the “unknown” in this situation was also hampering investigators. “We know very little going into this. We do not know if this was an accident or a deliberate act,” he said. “We have law enforcement conducting interviews, working with HAZMAT.” He noted that investigators were unable to talk with the two critically injured people, who were apparently closest to the scene.

He also said, “There was no indication of any sound or observation of vapor release” at the scene — and that people just became ill.

Fire Chief Paul Leger said a 911 call came in at 10:27 a.m. Monday, reporting that people working at the ABC plant had been overcome “for some unknown reason,” determined to be “some kind of release of a chemical we do not know.” Earlier in the day, police officials described that as “a dense vapor.”

He said the incident appeared to have happened in an area “where the garbage trucks back up to the hopper” and drop off their trash. When firefighters arrived, three workers “were laid out’ in front of that area, he said. Triage got under way, “and three needed immediate transport.”

Leger said the response quickly escalated to Level 4, which he described as “one below the highest level” of HAZMAT response.

The police blocked regular traffic to Shawmut Avenue as rescue trucks, private ambulances, fire trucks, and HAZMAT vehicles arrived throughout the day. State police, the state Fire Marshal’s Office, the Mass. Department of Public Health, the American Red Cross, the U.S. Environmental Protection Agency and Department of Environmental Protection were also among the responders.

All were brought through decontamination tents set up by the New Bedford Fire Department outside area hospitals, including St. Luke’s Hospital in New Bedford, and Charlton Memorial Hospital in Fall River where the injured were taken.

Dr. Paul Bulat, head of St. Luke’s and chairman of its emergency department, said yesterday afternoon that the two critically injured workers were undergoing diagnostic tests including for chemical exposure.

By early evening, St. Luke’s Hospital had received 66 patients, including ABC Disposal employees and many first responders, including EMS paramedics, police and firefighters, said Joyce Faria Brennan, public information for Southcoast Health System — which includes Charlton Memorial, St. Luke’s and Tobey Hospital in Wareham.

At that hour, approximately 10 patients were still being treated at St. Luke’s but were expected to be released soon, Brennan said. The remaining 52 patients had been treated and released. Another 53 victims were treated and released at Charlton Memorial Hospital, she said.

According to the company’s Web site, ABC Disposal Service Inc has been in business for 40 years. The company collects, transports and disposes of more than 200,000 tons of non-hazardous waste, according to company information available online.

New Bedford Police Detective Lt. Jeffrey Silva said that ABC is “a family operation” and “a partner in the community.” He said ABC is “very reputable,” has “been here a long time,” and that the facility is up to date and modern.

“Clearly this is an anomaly for them,” Silva said.

Mayor Scott W. Lang said ABC had been “100 percent cooperative” with the investigation. He also said the emergency response — practiced by regional drills — went smoothly. “The public can be assured that we are doing everything possible” to protect the community and get to the bottom of what happened.

tmooney@projo.com