Japanese police are hunting for a killer after two elderly men were poisoned at a hospital near Tokyo, local media reported Tuesday.

An autopsy showed that the deaths at a hospital in Yokohama were caused by a chemical found in antiseptic, according to public broadcaster NHK and other media. The police suspect that the serial posioner could be responsible for killing as many as 48 elderly people.

The chemical is the same as one in a disinfectant used at the Oguchi Hospital's nurse's station, Jiji Press news agency said, citing sources.

The investigation comes two months after the murder of 19 people at a centre for the mentally disabled, Japan's worst killing spree in decades.

In the latest case, media reported, police suspect fatal amounts of the chemical were injected into intravenous drips for the two 88-year-old victims, Sozo Nishikawa and Nobuo Yamaki. The men both died this month.

Police would not confirm their investigation.

In 2000 a male nurse was charged with killing one patient and attempting to murder four others by poisoning them at a clinic in the northern Japanese city of Sendai.