BOSTON -- The driver at the wheel when two Massachusetts Bay Transportation Authority trolleys collided in Newton last month was not on her cell phone at the time of the crash, officials announced Tuesday.

An MBTA Green Line trolley struck and crashed into the rear of another trolley on May 28 at about 6 p.m., injuring several people and killing trolley operator Terrese Edmonds.

Among other possible causes of the crash, investigators were trying to determine if Edmonds was using her cell phone at the time. But, after recovering Edmonds' cell phone and accessing her phone and text messaging records, officials determined that she was not on her phone.

"We issued legal process to access records of her phone calls and text messages as well as her Internet usage on the phone, and engaged in forensic analysis. We also spoke to witnesses who were able to observe the driver during the moments immediately leading up the crash. Based on that investigation, there is no evidence that she was in communication with anyone on her cell phone -- whether through phone calls, text messages, or e-mail -- in the time immediately leading up to the crash," Middlesex District Attorney Gerry Leone said in a statement.

Leone said that Massachusetts State Police detectives assigned to his office and MBTA transit police detectives have conducted a thorough investigation into the cause and circumstances of the crash. The investigation included interviews with multiple witnesses at the scene, forensic examination of evidence, analysis of the accident reconstruction performed by the MBTA, and an examination by the Chief Medical Examiner's Office.

"It is our determination that there is no evidence of criminal conduct by any of the survivors of the crash. Further, there is insufficient evidence of criminal conduct by the operator of the striking trolley car. Because there are no prosecutable crimes, our criminal investigation is now closed and no criminal charges will be brought," Leone said.

A preliminary examination by the medical examiner also determined that there was no indication of alcohol or other drugs in the driver's system at the time of the crash. A full toxicology report will take weeks for the medical examiner to complete.

MBTA General Manager Daniel Grabauskas said that officials will continue to work with the NTSB to determine a cause of the crash.