Two Delaware patients died last weekend after taking heparin, a widely-used blood thinner made by Baxter International Inc. (BAX), prompting a review of the drug and sparking concerns about a repeat of fatal heparin contamination in 2008.

The two deaths, which happened over the weekend, were confirmed by a spokesman for Beebe Medical Center in Lewes, Del. A third patient suffered medical problems as well. All three were using heparin supplied by Baxter, based in Deerfield, Ill., though there is no specific evidence tying heparin to the illnesses.

"We are not pointing fingers at Baxter," said Wallace Hudson of Beebe Medical Center. "We don't know what's going on, but heparin is the only commonality that we were able to see ourselves."

The hospital informed Baxter on Friday that three patients had become ill, said Baxter spokeswoman Erin Gardiner. She said in an interview that the company immediately contacted the Food and Drug Administration. Both Baxter and the FDA quickly sent medical teams to Delaware.

FDA spokeswoman Karen Riley said the FDA is actively investigating the incidents. She said based on the investigation so far these appear to be isolated incidents. The FDA and Baxter have tested some of the heparin and haven't found any problems with it, Riley said.

The patients who died were a 71-year-old man and a 64-year-old woman. Both were flown by helicopter from Beebe. One died at Christiana Hospital in Delaware and the other at University of Maryland Baltimore hospital. Their names weren't released by the hospital.

The situation isn't the same as last year's crisis in involving tainted Chinese supplies, Gardiner said. That problem was linked to roughly 80 deaths and led to a recall of heparin from several companies.

Gardner said the new complications involve pre-mixed intravenous bags of heparin. Last year's problems involved bulk supplies, vials of the medicine and drug-coated medical devices.

Second, there are no Chinese suppliers involved, she said.

"There is one lot of heparin we are focusing on, from a North American source," Gardiner said. "It was not produced by Chinese manufacturers."

Third, Baxter tests on the Delaware incidents didn't detect a contaminant found in last year's heparin illness outbreak. That contaminant, over-sulfated chondroitin sulfate, wasn't identified in the latest case.

Finally, the injured patients this time have suffered inter-cranial bleeding, Gardiner said. Last year, the outbreaks mostly involved allergic reactions and cardiac complications.

-By Alicia Mundy, The Wall Street Journal, and Jared Favole, Dow Jones Newswires. 202-862-9243. alicia.mundy@wsj.com