Investigators returned to Tewksbury Tuesday for the third time as they search for evidence in an ongoing criminal investigation, the details of which law enforcement are keeping under wraps for now.
The search was launched Monday on Livingston Street near the grounds of the Tewksbury Hospital, officials said. Middlesex District Attorney Marian T. Ryan’s office is overseeing the inquiry, but would not provide any details of the probe or what case is being investigated.
“The police activity is connected to an ongoing investigation and is not connected to a recent event,’’ Ryan spokeswoman Meghan Kelly wrote in an e-mail to the Globe. “We are unable to confirm any additional details at this time to protect the integrity of the investigation.”
Kelly said there is no threat to the public.
Police first searched the area on Dec. 29, returned on Monday with heavy excavation equipment, and are expected to be on site for a period of time Tuesday, Kelly said. Police also used cadaver dogs on Monday to search the area, she said.
No further details are currently available.