(CNN) Ten people at a care facility in Oklahoma were hospitalized after they were injected with insulin instead of a flu shot, police said.

Eight of the patients were residents of Jacquelyn House and two were employees, Sgt. Jim Warring, with Bartlesville Police Department told CNN. The facility serves intellectually and developmentally disabled people, according to the website of AbilityWorks, the company that owns the eight-resident site.

EMS and fire crews responding Wednesday afternoon "found ... multiple unresponsive people," police Chief Tracy Roles said during a news conference covered by CNN affiliate KTUL.

Most patients' suffering symptoms after the medication was administered "were not able to explain the issues," Warring said. "Many of them are not vocal and not able to walk."

"All these people are symptomatic, lying on the ground, needing help, but can't communicate what they need," Roles said. "That's why I give a lot of praise to the fire and EMS staff for doing an outstanding job of identifying the problem."

The pharmacist who injected the insulin was a contractor and went to the facility on Wednesday to administer the flu shot to residents and employees, Rebecca Ingram, CEO of AbilityWorks of Oklahoma, said in a statement.

Ingram said all people who received the injection had reactions and were taken to Jane Phillips Hospital in Bartlesville.

Several remained hospitalized Thursday due to the long-acting insulin that was administered, police said.

Ingram didn't discuss whether the residents and employees were injected insulin but said authorities were investigating the "cause of the reactions to the injections."

"I've never seen where there's been some sort of medical misadventure to this magnitude," Roles said. "But again, it could have been a lot worse. Not to downplay where we are, but thinking about where we could be, it could certainly have been very, very tragic."

Tony D. Sellars, director of communications for the Oklahoma State Department of Health, said his agency will review the facility's report on the incident "to determine if we need to follow up or if their action was sufficient."

"There is no reason to suggest at this point that the facility should have had a reasonable suspicion that this sort of error would occur or be preventable on their part," Sellars said.

An investigation was still underway on Thursday.