A Los Angeles hospital's neonatal and a pediatric intensive care units won't reopen until the cause of a virulent infection is found, health officials said.

White Memorial Medical Center officials said at least seven children were sickened by and one probably died from an outbreak of Pseudomonas aeruginosa, the Los Angeles Times said Saturday.

Neither unit will accept new patients until "we believe it is safe for the patients to be admitted," said Rosalio Lopez, the hospital's chief medical officer. Other sections of the hospital were unaffected.

The suspected cause -- improper cleaning of a piece of equipment -- was being investigated by local, state and federal health investigators.

Lopez said the hospital tightened its infection control practices and notified patients' families in the affected units. As a precaution, the hospital administered antibiotics to all babies in the neonatal unit.

Pseudomonas aeruginosa, a common bacterium found in water and soil, can be spread through body contact, fluids and water. It usually is not deadly or dangerous, because people's immune systems can fight infection.

If the immune system is weak, the bacterium may cause respiratory, urinary tract and blood infections, among others.