PITTSFIELD — Multiple people are dead this week in what one first responder calls the worst wave of overdoses in years.

"We definitely saw more activity this week than we had in a long time," said Brian Andrews, president of County Ambulance.

The ambulance service responded to at least 10 suspected overdoses since Sunday, Andrews said Friday, including nine in Pittsfield and one in Dalton. He said he suspects that the string of overdoses resulted in at least two deaths in Pittsfield, citing one case of cardiac arrest and a person who was dead upon first responders' arrival.

There also was a report of an apparent heroin overdose death this week from the town of Adams, said Dennis Yusko, a spokesman for the Berkshire District Attorney's Office. Department of Public Health statistics show that 40 people died last year from an opioid-related overdose in the Berkshires.

It's hard to say definitively what happened this week until lab results come back. Still, Andrews said the spike was enough to sound the alarm for the Pittsfield Police Department and health care officials. He said he reached out this week.

"There's something going on, but we don't know what it is," he said.

Unlike with previous upticks, Andrews said, his staff hasn't seen evidence implying there's a particularly dangerous batch of opiates making the rounds. And he said there's nothing about the time of year that would explain such a rise.

"It's not really cyclical according to the year," he said. "So, there's nothing you can look at to justify it."

The Pittsfield Police Department did not provide overdose statistics Friday.

Pittsfield Fire Chief Robert Czerwinski confirmed that the overdose volume raised hairs within the department this week.

"We've had an extremely busy week," he said.

Czerwinski said his team administered Narcan on three of the calls this week. Andrews said that not every overdose victim gets a dose of Narcan, citing "strict" protocols about only administering the opiate blocker if the person is not breathing.

Berkshire District Attorney Andrea Harrington said in a statement that her office is working to combat the issue by targeting drug trafficking and implementing harm-reduction strategies for those suffering from substance use disorder. More must be done, she said.

"We are losing the fight against addiction in Berkshire County with tragic and devastating consequences," she said.

The uptick so far appears to be a central Berkshire phenomenon. North Adams and Great Barrington each has registered one overdose this week, according to respective law enforcement officials.

"It hasn't been too busy for us," said Great Barrington Police Sgt. Adam Carlotto, noting that the one overdose in Great Barrington was not fatal.

It wasn't clear Friday whether the overdose this week in North Adams proved fatal.

Amanda Drane can be contacted at adrane@berkshireeagle.com, @amandadrane on Twitter, and 413-496-6296.