The Rockefeller Files: Scientists at University Menaced : Crime: Someone has poisoned researchers’ drinks, left gas jets on, set a fire and mailed threats. Police suspect a disgruntled employee.

Over the years, scientists at Rockefeller University--one of the world’s preeminent research institutions--have identified DNA, found the first cancer virus, grown the malaria parasite and wrestled with some of biology’s most complex problems.

Now, they are trying to solve their most terrifying mystery: Who may be trying to kill them?

Police revealed Tuesday that someone at the research campus bordering the East River in Manhattan put poison in coffee and tea, deliberately left gas jets on in a molecular biology laboratory, set a fire and sent threatening letters to two eminent women scientists.

The events over five days in June, first detailed in Tuesday’s Wall Street Journal, have spread fear through portions of the university, which over the years has produced 19 Nobel Prize winners. Laboratory workers have taken lie detector tests and have been questioned extensively by police.

“We believe it’s a disgruntled employee,” said John Hill, chief of Manhattan detectives. “We’re working on the theory it’s jealousy of these two women . . . We have a suspect in mind.”

Hill said the letters demanded that the two scientists quit.

“It’s my opinion the person who is responsible for these acts is an employee there still,” the detective chief said. He declined to identify the scientists who were menaced.

Events at the university, founded by John D. Rockefeller in 1901 after his first grandchild died from scarlet fever, center on the molecular biology laboratory headed by Prof. Robert Roeder, a noted researcher.

Police said that on June 6 a group of workers in the 15th-floor laboratory became ill after drinking tea and coffee. At first, the scientists believed that cream or the sugar, which tasted bitter, had become tainted. But as the illnesses worsened and events progressed, it became clear that the beverages had been poisoned.

The next day, gas jets were left on in Roeder’s laboratory, which could have caused an explosion. Workers closed the valves and no one was injured.

On June 8, a small fire was discovered in a closet. Paper towels were smoldering as a result of arson. Two days later, letters containing death threats to the two scientists were found in a women’s restroom. Two more letters were sent to Roeder and to Rockefeller University officials.

“They were threatening in nature. They wanted them to quit,” Hill said. The letters also contained chilling news for the biologists, all of whom had recovered from the tainted brew. The letters confirmed that the tea and coffee had been poisoned with sodium fluoride, which in greater concentrations could kill. Sodium fluoride was one of the chemicals stocked in the molecular biology lab.

Hill said investigators believe that the poisoning was designed to be a warning. “There were many chemicals that could kill you instantly in that lab,” he said.

For more than a month, police and Rockefeller University security officials conducted a quiet investigation. That became increasingly difficult as word of the troubling events at Rockefeller spread to other research institutions.

Officials at Rockefeller University said security precautions had been increased at Roeder’s basic genetics laboratory, where 40 scientists and technicians work in the Tower Building. A spokesman declined to elaborate on the preparations.

Detectives believe that professional jealousy is behind the attacks. Although it is built in a quiet, park-like setting with towering trees, spacious lawns and a tennis court on Manhattan’s upper East Side, Rockefeller University is a highly competitive place. There are no undergraduates, only graduate students. Pressure to produce is intense.

“The people who are working there are the cream of the crop,” Hill said.

“It’s jealousy. It’s obviously jealousy,” the Manhattan detective chief said. He said both scientists were “at the top of their field,” and indicated that the threats in the notes were not subtle. “You clearly understand what the meaning was,” Hill said.

He said investigators were following the theory that one person was behind the incidents. He said not only had lie detector tests been administered to some scientists and technicians, but also in some cases blood samples had been taken in an attempt to link DNA from the blood to any clues left by the culprit.

“We have a suspect in mind,” he told reporters gathered in a police station. “I believe he is one of the 40.” Hill declined to say whether the suspect had taken a lie detector test.