FBI and postal officials announced yesterday that they will mail 500,000 fliers to residents in the Trenton, N.J., area in an attempt to flush out suspects in their foundering anthrax investigation.

Officials also announced at a Ewing, N.J., news conference that they had doubled the reward in the case to $2.5 million.

In a separate announcement, the FBI said it was launching a massive effort to recruit more than 960 new special agents over the next eight months. Most would be focused on counterterrorism, counterintelligence and scientific analysis.

FBI officials said the hiring campaign, one of the most aggressive they have ever mounted, would increase the total number of FBI agents by more than 8 percent and nearly match the growth of the force over the past 10 years. The bureau currently has more than 27,000 employees, including more than 11,000 agents.

The FBI is seeking to recruit agents with experience in -- among other specialties -- terrorism, intelligence and underrepresented languages such as Arabic, Farsi and Pashto, officials said. The hirings are meant to enhance the FBI's "ability to address terrorism and homeland security," according to a statement.

The FBI and the U.S. Postal Inspection Service, meanwhile, signaled a renewed focus on the central New Jersey area as they try to find the culprit in a spate of anthrax mailings that killed five people and sickened 13 others.

Authorities have recovered four letters laced with anthrax bacteria that passed through a postal distribution center in Hamilton Township, N.J., near Trenton, leading investigators to believe that the sender likely has some connection to the area.

The half-million fliers will be mailed to residents of central New Jersey and Bucks County, Pa., asking for help, and will include pictures of the envelopes used in the anthrax attacks, officials said.

Kevin Burke of the U.S. Postal Inspection Service said the "individual responsible for these acts may well be a neighbor, may be a work associate" of central New Jersey residents.

The doubling of the reward in the case, from $1.25 million to $2.5 million, includes $500,000 from direct mailer Advo Inc., one of the largest users of the postal system. Although the company recently reported lower fourth-quarter earnings, a spokesman said Advo "has seen no direct financial impact of the anthrax attacks."