And one of the letters that has been a focus of the anthrax investigation in Florida came with a Star of David inside.

Several experts, including some on whom the F.B.I. has relied, said the anthrax investigation had taken some wrong turns.

American Media executives, who had been highly critical of officials' handling of the anthrax investigation, declined to comment on the test results beyond a statement.

Several developments stand out in Mr. Preston's account of the anthrax investigation.

Instead, they said it may end up with thousands of false leads that have dogged the anthrax investigation since early October.

In the end, two months into the oldest component of the anthrax investigation, frustrations predominate.

Dr. Hatfill has been subjected to greater scrutiny than anyone else in the anthrax investigation, but the government has brought no charges.

Experts and officials remained reluctant yesterday to discuss details of the anthrax investigation.

First is the F.B.I.'s initial slowness in carrying out the anthrax investigation.

It is another curious twist in the anthrax investigation, which has confounded medical experts from the start.