But the investigation, which began in 1998, has yielded few actual prosecutions.

The investigations did not yield evidence of criminal conduct.

It was not clear on Friday how a new investigation could yield information that years of legal proceedings had failed to.

Tomson called to say that further investigation had yielded no leads.

Thus far, the investigation has yielded two indictments and one conviction.

In all, a drug agency official said, the investigation yielded 18,000 marijuana plants over the two years with a wholesale value of $17 million.

By relying on such a process, the directors may not obtain the kind of information an independent investigation would yield, experts said.

The head of the court panel said the investigation had yielded no evidence of a criminal organization.

It was first believed to be arson but investigations into the fire have yielded no results.

The government even asked other countries for help, but the investigation has yielded no results to date.