According to the Health Minister Camilo Alleyne, kidney and nervous tissue damage was detected by the tests conducted on the 18 victims, which suggested poisoning.
"The studies of kidney and nervous tissue showed damage that suggests a toxic effect," Mr Alleyne said, saying there were no signs that the sickness was contagious.
The mysterious illness was reported first a month back and it seems to affect the elderly men undergoing treatment for high blood pressure, diabetes and kidney disorders. Most of them were taking several treatments at a time.
Health Minister Camilo Alleyne said, "Officials are recalling Lisinopril tablets from pharmacies, hospitals and private clinics across Panama as scientists are testing the drug for toxic agents that may have poisoned 30 people."
"The cause is still not completely confirmed," Alleyne told a news conference late on Friday. "We decided as a safety precaution to withdraw this medicine from use."
"Some 7,000 Panamanians have public health service prescriptions for Lisinopril."
The number of private patients on this drug is not known.
Scientists from Panama and the U.S. working on the case have rejected diseases like dengue fever, influenza and West Nile virus.