(CNN) -- A Missouri VA hospital is under fire because it may have exposed more than 1,800 veterans to life-threatening diseases such as hepatitis and HIV.

John Cochran VA Medical Center in St. Louis has recently mailed letters to 1,812 veterans telling them they could contract hepatitis B, hepatitis C and human immunodeficiency virus (HIV) after visiting the medical center for dental work, said Rep. Russ Carnahan.

Carnahan said Tuesday he is calling for a investigation into the issue and has sent a letter to President Obama about it.

"This is absolutely unacceptable," said Carnahan, a Democrat from Missouri. "No veteran who has served and risked their life for this great nation should have to worry about their personal safety when receiving much needed healthcare services from a Veterans Administration hospital."

The issue stems from a failure to clean dental instruments properly, the hospital told CNN affiliate KSDK.

KSDK: VA dental patients at risk of infection

Dr. Gina Michael, the association chief of staff at the hospital, told the affiliate that some dental technicians broke protocol by handwashing tools before putting them in cleaning machines.

The instruments were supposed to only be put in the cleaning machines, Michael said.

The handwashing started in February 2009 and went on until March of this year, the hospital told KSDK.

The hospital has set up a special clinic and education centers to help patients who may have been infected. However, Carnahan said he feels more should be done and those responsible should be disciplined.

"I can only imagine the horror and anger our veterans must be feeling after receiving this letter," Carnahan said. "They have every right to be angry. So am I."

This is not the first time this year a hospital has been in hot water for not following proper procedures.

In June, Palomar Hospital in San Diego, California, has sent certified letters to 3,400 patients who underwent colonoscopy and other similar procedures, informing the patients that there may be a potential of infection from items used and reused in the procedures.