UPDATE 11:43 a.m.: A massive 2004 program to partially replace lead water mains across the District of Columbia because of concerns about tainted water actually made the the problem worse, utility officials confirmed Thursday.

DC Water held a news conference to respond to a report by the Centers for Disease Control and Prevention.

The report concluded that children, pregnant women and those with compromised immune systems were at risk in the 14,800 D.C. homes where a lead service line had been replaced, but the homeowner declined to change the pipe between the service line and the faucet. (Timetable of lead pipe replacements. )

Only about 2,800 homeowners volunteered to pay for replacing the water pipes between the street and their home faucets.

DC Water also said there was a spike in lead levels after the Washington Aqueduct changed the chemical it used to treat water. That chemical, cholarmine, is blamed for leaching lead out of pipes and putting it into the water supply. DC Water says lead levels have declined since the chemical was changed.

Brigid Gutmacher says the water main on her street recently ruptured and was replaced. She says she has new concerns about her water after reading the CDC's report.

"I have a family member with immune problems, so I'm getting (my water) tested," she said.

DC Water says the partial replacement of lead water mains "rattled" the system, essentially shaking loose lead that was able to enter the water supply.

ORIGINAL POST: DC Water will host a press conference Thursday following a recent report by the Center for Disease Control claiming water in thousands of D.C. homes may be contaminated with lead.

The conference is scheduled for 10:30 a.m. at the front entrance of DC Water’s headquarters, located at 5000 Overlook Avenue, SW.

The Washington Post reported Wednesday that nearly 15,000 homes that received new pipes because of lead contamination may still be contaminated.

The CDC says partial pipe replacements may have made the problem worse.