Tokyo » Authorities in Japan are investigating the poisoning deaths of two elderly patients at a Yokohama hospital specializing in terminal-stage care.

Oguchi Hospital has had a higher death rate in recent months, sparking speculation that the poisoning may have been systematic and more widespread.

The case surfaced Sept. 20 when the hospital informed police of a possible poisoning after an 88-year-old man died while receiving an intravenous injection. Police confirmed Nobuo Yamaki’s IV solution had been contaminated with a disinfectant.

He turned out to be the second victim. Police rushed to get hold of the body of his former roommate, who had died two days earlier, before it was cremated. An autopsy showed he had been poisoned with the same chemical.

Investigators also reportedly found tiny puncture marks in 10 of about 50 unused intravenous bags stored at the nursing station on the fourth floor, which handles the terminally ill. The pinholes were on a protective seal covering each rubber cap where an IV tube connects.

Police confiscated the bags, along with syringes and other equipment, but have not released findings.

A lawyer for the hospital, Yuki Uehara, told The Associated Press that 46 other patients had died on the same floor from July 1 to Sept. 20.

The fourth floor can handle up to 42 patients at a time, and normally about half die while hospitalized, Uehara said. Including the two recent deaths, the 48 exceeded 60 percent, somewhat above average but not an abnormal spike, he said.

Hospital chief Yoichi Takahashi told reporters last month that “we see many people pass away due to the nature of this hospital, but I had an impression that the number of deaths was somewhat larger than usual.”

He said his biggest concern was a massive infection but that possibility was ruled out after checking. When asked, he said he could not rule out criminal activity. He did not elaborate.

Uehara said the hospital has been admitting patients who are more seriously ill than usual, and that could also explain the higher death rate.

In July, Yokohama officials received an anonymous email about suspicious incidents at the hospital: nurses’ aprons torn, a bottled drink laced with bleach and a patient’s card missing. Tetsuo Hama, the manager of the city’s medical affairs department, said officials had thought they were internal harassment cases.

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This story has been corrected to show that investigators, not hospital staff, found puncture marks in intravenous bags.