Chile's public health system may have failed to notify at least 512 people that they were infected with the HIV virus, Health Minister Alvaro Erazo said Thursday amid a mushrooming AIDS scandal.

Appearing before Chile's Lower House of Congress, Erazo said public health system records could not confirm that some 244 people infected with the virus had been informed, despite efforts to the contrary.

Records also could not show efforts had even been made to inform another 268 people, according to a Health Ministry document issued on Erazo's presentation to Congress.

"With current information it is not possible to be sure that people identified in the ... groups have not been informed, only that there are no records of that happening," he said.

Chile's previous health minister resigned and was replaced by Erazo after it emerged a hospital in far northern Chile failed to notify dozens of patients that they had tested positive for HIV.

Before she quit when the scandal broke last month, Maria Soledad Barria removed the head of medicine, the supervising nurse and the head of the blood bank at a hospital in Iquique in northern Chile pending an investigation into possible negligence.

Erazo told lawmakers Thursday the government would take immediate action to revise public health system procedures and protocol.

Chile President Michelle Bachelet's center-left coalition government has been battered by protests and scandals in recent months, helping boost its rightist rivals ahead of what is seen as the toughest presidential race since the return to democracy two decades ago.

Bachelet, who trained as a doctor and was a former health minister, is an AIDS expert.