WINDHAM, Conn. (AP) — Police are investigating a batch of synthetic marijuana that sickened about a dozen people, sending several to the hospital.

Cpl. Stanley Parizo Jr. with the Willimantic Police Department said they began receiving calls Monday morning of people exhibiting psychotic behavior after smoking the drug commonly known as "K2" or "Spice."

"We've seen people running around without shirts, running down main thoroughfares within the city, asking for help," he said.

Parizo said they are trying to track down the source of the synthetic marijuana, which police believe may have been laced with the hallucinogenic PCP. Samples have been sent out to a laboratory for testing, he said.

Karen Butterworth-Erban, the Eastern regional director of emergency services for Hartford Health Care, said five people, ages 22 to 42, were brought to Windham Hospital on Monday. Four of them have since been released.

She said there may have been other cases in Willimantic linked to the drug, but because synthetic marijuana is not detectable through toxicology screens, doctors don't always make a connection if they are not told the person had been using K2.

Butterworth-Erban said it was not immediately clear what was in this batch of K2, but the symptoms from Monday were consistent with other cases the hospital has dealt with in recent weeks.

"The chemicals that are added to the plant material certainly cause some mind-altering effects," she said. "We are going to see agitation, confusion, hallucinations."

She said the drug has been a problem for a couple of years, but there has been an uptick in the region since March.

"There has not only been an increase in cases but an increased in enhanced presentations," she said.