Two male nurses in Uruguay have been charged

The men were held after a two-month police investigation. A third nurse was charged with concealing evidence.

The judge in the case said the two admitted to a total of 16 induced deaths, but they could be responsible for dozens more.

A lawyer for one nurse said her client had acted for humanitarian reasons.

He is "aware of his actions" and had "confessed fully to the judge", lawyer Ines Massiotti said.

Prosecutors say the alleged killings took place in the cardiology unit of the Maciel Hospital and in the intensive care unit of the Spanish Mutual Care hospital.

'Psychopathic behaviour'

The names of the nurses - who were apparently not working together - have not been released.

Reports in Uruguay's media suggest that as many as 50 people could have been killed through a combination of administered medication and other procedures.

Police inspector Jose Luis Roldan said poison from Brazil had been used on patients who were in critical condition, the Associated Press news agency reports.

However, investigators believe that not all the victims were terminally ill.

A spokesperson for one of the hospitals involved said that the deaths were the consequence of "psychopathic behaviour".

Forensic studies are still being carried out and the results could take several days, the BBC's Vladimir Hernandez reports.

Uruguay's public health ministry issued a statement saying it was co-operating with the investigation into "presumed criminal acts linked to the health area".

It expressed "profound concern" over the case and said it was carrying out its own investigation.