Eight months have passed since the Department of Homeland Security took over the management of Plum Island from the Agriculture Department. Last week, Homeland Security officials offered a rare glimpse into this veiled and mysterious island. The timing of the tour for a dozen journalists coincided with the publication of a new book, ''Lab 257,'' by Michael Christopher Carroll, who argues that the Plum Island laboratories have an appalling safety record and can be linked to outbreaks of Lyme disease and West Nile virus. There have long been questions about the safety of Plum Island's operations, but they became more prevalent after the Sept. 11 terrorist attacks. Mr. Carroll, a lawyer from Bellmore, writes that in 2002 American forces in Afghanistan found a file on the Plum Island laboratory in the home of a nuclear physicist identified by American officials as an associate of Osama bin Laden. Mr. Carroll, who calls the lab a ticking biological time bomb, describes low employee morale and a decline in security after a private company took over support functions in 1991. A report from the General Accounting Office released in October also criticized security at the center, saying that officials did not control access to dangerous pathogens that could be adapted for germ warfare. The report also cited door alarms and sensors that did not work ... and insufficient background checks. Plum Island and Homeland Security officials said there have been no direct terrorist threats against the lab, which studies foot-and-mouth disease and swine fever, among other diseases.