A hospital in Yokohama where police suspect two people were fatally poisoned through their intravenous drips this month, has recorded 48 deaths since July of patients who had stayed on the same floor, sources close to the matter said Thursday.

There were some days around mid-August and mid-September when four or five people died, but Oguchi Hospital could not confirm any hospital infections and thought the reason was because it had been accepting more seriously ill patients, the sources said.

The hospital in Yokohama’s Kanagawa Ward has 85 beds and specializes in internal medicine, orthopedics and rehabilitation for the elderly. It has also been accepting more patients in the terminal phase of their illnesses.

Police will investigate the patient deaths, but are unlikely to be able to specify the causes because many of the bodies have already been cremated.

“We see many people pass away due to the nature of this hospital, but had the impression that the number of those dying was increasing a bit,” a hospital official said.

It was not immediately known how these figures compare with deaths in other hospitals catering to patients with similar diseases or at a similar age.

The hospital first alerted the police about the possibility that intravenous drips had been tampered with on Sept. 20. The police have so far determined that two 88-year-old male patients — Nobuo Yamaki and Sozo Nishikawa — were poisoned. A surfactant compound is believed to have been used to kill them.

Surface acting agents are widely used in hospitals as disinfectants, but can be poisonous.

On Thursday, the hospital also began conducting blood tests on other patients on the fourth floor, where Yamaki and Nishikawa stayed, to see if any poisons could be detected.

Investigators have found small holes in seals on the rubber plugs of some 10 unused drip bags stored at the nurses’ station at the hospital.

Some bags bore the names of patients other than the two killed. Police suspect someone, possibly an insider, was trying to kill patients indiscriminately.