An investigation into several patient deaths at DaVita Lufkin Dialysis Center has expanded from a 30-day period to 18 months as state health officials and local law enforcement comb through more than 200 patient records, said a public health spokeswoman Monday.

"There is a lot of work being done and a lot of concern for the patients in this community," said Sharon Shaw, administrator of Angelina County and Cities Health District.

DaVita shut down its facility at 700 S. John Redditt Drive April 28 after contacting officials at the Texas Department of State Health Services and Lufkin Police Department about a recent spike in patient deaths.

Officials are not releasing the number of patient deaths at the center because the time period of the investigation keeps changing, Shaw said.

The facility is expected to be shut down a minimum of 45 days — part of a regulatory agreement with the state — while officials pore through dozens of documents, interview patients and send off lab equipment and water used at the facility to test for contamination, the spokeswoman said.

Most dialysis patients are typically frail and in poor health when they begin undergoing treatments, so officials are considering everything in determining the causes of death, Shaw said.

"We'd like to ease people's minds that everything is being looked at," she said, calling this point in the investigation the "information gathering stage."

As of last week, a Lufkin police spokesman said there does not appear to be any criminal involvement surrounding the deaths.

"It is not known at this time what may have caused the unexpected deaths and complications, but no evidence of criminal activity has been found," said Lt. David Young, in a statement released last week.

The investigation involves approximately two dozen officials from the Center for Disease Control and Prevention, Centers for Medicare and Medicaid Services, DSHS and LPD, Shaw said.

A dozen of those officials are working from offices at DaVita Lufkin and the health district while another dozen officials are available by phone, the spokeswoman said.

DaVita, Inc., is a nationwide kidney care service company that serves more than 100,000 patients in 43 states at its more than 1,300 outpatient facilities, the release stated.

More than 120 patients have been sent from the Lufkin center for care at DaVita facilities in Henderson and Livingston and Nacogdoches, a company spokeswoman said last week.