BOSTON (Reuters) - Pfizer Inc has received grand jury subpoenas from the U.S. Justice Department in connection with an antitrust investigation focusing on drugmakers that market intravenous saline solutions.

FILE PHOTO - The Pfizer logo is seen at their world headquarters in Manhattan, New York, U.S., August 1, 2016. REUTERS/Andrew Kelly/File Photo

The drugmaker disclosed the subpoenas in a statement on Wednesday after ICU Medical Inc, which recently acquired Pfizer’s global infusion therapy business, and Baxter International Inc said they received similar subpoenas.

ICU Medical said the probe related to Hospira Infusion Systems, which it purchased in February from Pfizer, which in turn acquired it in a merger with Hospira Inc in 2015.

“Pfizer can confirm that it has received grand jury subpoenas in connection with an investigation by the U.S. Department of Justice, Antitrust Division and we are evaluating the requests,” Pfizer said.

A Pfizer spokeswoman said the probe related to intravenous saline solutions. The Justice Department declined to comment.

The probe comes amid a shortage of intravenous saline solutions commonly used to hydrate hospital patients that dates back to late 2013, when drug companies began notifying hospitals that they might experience delivery delays.

The U.S. Food and Drug Administration in January 2014 added the solutions to its drug shortage list, at the time saying the shortage was triggered by factors including increased hospital demand, potentially related to the flu season.

In 2015, a bipartisan group of four U.S. senators asked the Federal Trade Commission to probe three companies they said supplied all the saline solution used in the United States, Baxter, Hospira and B. Braun.

They said that since the shortage began, prices had risen 200 percent to 300 percent.

Democratic Senator Richard Blumenthal of Connecticut, one of the four senators, on Wednesday called the Justice Department’s probe “an important step toward getting to the bottom of any possible illegal collusion by saline solution manufacturers.”

On Friday, Baxter said one of its employees received a grand jury subpoena issued by the U.S. District Court for the Eastern District of Pennsylvania. ICU Medical on Tuesday said it received a similar subpoena.

ICU Medical and Baxter said the subpoenas sought documents and testimony about the manufacturing, selling, pricing and shortages of intravenous solutions, including saline, and communications with competitors.

Baxter and ICU Medical have said they are cooperating with the probe and that they have also received information requests from New York Attorney General Eric Schneiderman.

Baxter and Hospira also face a proposed class action lawsuit accusing them of conspiring to fix prices for intravenous saline solution.