Seven patients have died and several more have been made ill at a hospital in Setagaya Ward, Tokyo, from what is believed to be an infection spread within the facility, the institution said Friday.

The two male and five female patients at Ito Noshinkei Geka Byoin (Ito Neurosurgical Hospital) who died between Jan. 10 and Wednesday may have succumbed after being infected with serratia bacteria.

According to the Health, Labor and Welfare Ministry, Tokyo Metropolitan Government officials have conducted inspections of the hospital as stipulated under the Medical Service Law.

Of the seven patients, one was a 24-year-old woman while the six others were 60 or older, including one 91-year-old, the hospital said.

The Tokyo Metropolitan Research Laboratory of Public Health is conducting genetic research to determine whether all of the patients contracted the same strain of the bacteria. Results are expected by early next week, officials said.

The hospital reported the deaths to a local public health center Tuesday.

The center has confirmed that six patients, including two who have died, were infected with serratia bacteria and suspects they were infected from the same source.

The hospital suspects that a total of 12 patients, including the seven who have died, were infected. The conditions of the five others are improving, it added.

If confirmed, it will be the third case of in-hospital infection of serratia bacteria in Japan, according to the ministry.

Five people died after being infected with serratia bacteria in Tokyo's Sumida Ward in 1999, while seven were killed in a similar outbreak at an institution in Sakai, Osaka Prefecture, in 2000.

During a news conference at the metropolitan government building Friday afternoon, questions focused on the time lapse between the outbreak of the infection and the hospital's report to health authorities.

By the time the hospital alerted the Setagaya Ward Office on Tuesday evening, five days had passed since the first two patients had died and the death toll had already reached six.

"Retrospectively, it is regrettable," a metro official said. "I wish the hospital had recognized that it's an emergency situation on Monday (when the total number of the deceased reached five)."

The metro officials became defensive when asked why a a news conference was not held until after the hospital had made its belated public announcement, saying it was their policy to make the hospital to come forward voluntarily.

The Ito hospital started operating in November 1996 and has 33 beds. It specializes in neurosurgery, internal medicine and orthopedic surgery.

Serratia bacteria, which live in human intestines and also commonly exist in the air or on the palms, rarely affect healthy people but may cause inflammation of the bladder or the kidneys in people whose immune systems have been weakened through old age or as a result of recovering from surgery.

The bacteria are believed to be resistant to almost all antibiotics and can cause life-threatening blood poisoning if they enter the bloodstream.

Keiichi Hiramatsu, a professor of bacteriology at Juntendo University, said it is quite unusual for someone in their 20s to die from an infection of the bacteria.

Hiramatsu said the infection may have been caused by human error, such as insufficient sterilization of medical equipment.