OKLAHOMA CITY - The investigation widens into the Scientology based rehab center Narconon Arrowhead. 

Narconon's flagship rehab center on Lake Eufaula has been under investigation ever since three people died at the facility during a nine month time period in 2011 and 2012. Sources tell News 9 the Oklahoma Multi-County Grand Jury will now also be investigating the facility.  

The multi-county grand jury will meet next week. What they are investigating is typically kept secret. However, a former Narconon executive tells News 9 he has been subpoenaed to testify.

"I know all the top players personally. I've been with Narconon 13 years, so I know everyone all over the country," said Eric Tenorio, who spoke to News 9 from New York where he currently lives.

Tenorio says sheriff's deputies delivered a subpoena to his home and he has since learned he will be flown to Oklahoma City to testify in front of the grand jury on June 25. He says he doesn't know the specific nature of the investigation, but says he has been working with the Oklahoma Insurance Commissioner's office for months and believes that's what he will be testifying about.

"I've had conversations with Gary Smith and email exchanges with him about setting it all up so that what Narconon does can translate into billing codes," said Tenorio.

The Pittsburg County Sheriff and Oklahoma Department of Mental Health and Substance Abuse have investigated the facility, but so far nothing has come of those investigations. Tenorio says he hopes this will be different.

"I want it to not be a drawn out process like it has been. I want swift action."

A spokesperson from the Insurance Commissioner's office says they cannot comment on if they are investigating or if anyone in their office has been subpoenaed to testify.

The AG's office also says they can't comment on if an investigation into Narconon will be considered by the multi-county grand jury.