A radical group that opposes nanotechnology has has claimed responsibility for at least two bombing attacks on researchers in Mexico and it praises the "Unabomber," whose mail-bombs killed three people and injured 23 in the United States.

A manifesto posted Tuesday on a radical website mentions at least five other Mexican researchers whose work it opposes, and lauded Theodore Kaczynski, who is serving a life sentence for bombs that targeted university professors and airline executives.

It was issued in the name of a group whose title could be translated as "Individuals Tending Toward the Savage."

Mexico State prosecutors' spokesman Sonia Davila said authorities are investigating the authenticity of the manifesto, but said its description of how the dynamite-stuffed pipe-bomb was constructed matched evidence found at the scene of a small explosion Monday at Monterrey Technological Institute's campus in the State of Mexico, on the outskirts of the capital. Officials had not revealed details of the device that injured two professors.

The attacks caused some universities to take extra security precautions Wednesday. Officials at the campus hit by Monday's bombing said that metal detectors would be used at access points, vehicles entering the campus would be inspected, dogs would be used to detect suspicious artifacts, visitors would have to have an escort while on campus and student or faculty IDs would be required to enter the campus.

A police bomb squad removed a suspicious package left Tuesday at a Mexico City research institute, but an institute spokeswoman later told local media the package simply contained books.

Nanomaterials are made of extremely tiny particles, some thousands of times finer than a human hair, which have come increasingly into use in recent years, often in products such as skin care and cosmetics. Consumer advocates and others have raised questions about potential risks from these materials.

The manifesto expressed fears that that nanoparticles could reproduce uncontrollably and form a "gray goo" that would snuff out life on Earth.

"When these modified viruses affect the way we live through a nano-bacteriological war, unleashed by some laboratory error or by the explosion of nano-pollution that affects the air, food, water, transport, in short the entire world, then all of those who defend nanotechnology and don't think it is a threat will realize that it was a grave error to let it grow out of control," according to statement.

The manifesto said Monday's bomb was directed at professor Armando Herrera Corral, who is listed on the university's web site as a specialist in information technology. But the group also expressed satisfaction that professor Alejandro Aceves Lopez, an expert in robotics technology, was also injured in the Monday blast. Prosecutors say Herrera Corral brought the package to his colleague's cubicle to show it to him, when it exploded.

The university said both professors are recovering from their injuries.

The statement also claimed responsibility for attacks at another university in April and May against professor Oscar Camacho, listed by Mexico's National Polytechnical Institute as a specialist in micro-electro-mechanical systems.

The statement said a maintenance worker's "police impulses" to inspect the package triggered the bomb sent in May, causing minor injuries to the worker, not Camacho.

The federal Attorney General's Office described the attackers as an anarchist group and recommended universities step up security measures.

Jorge Lofredo, an Argentine expert on regional armed movements, noted that the group appears to be relatively new. He said that most anarchist groups avoid violent acts, and noted that previous Mexico City blasts blamed on anarchists were small and sought to avoid causing injuries.

Several Mexico City bank offices have been hit in recent years by small bombs made from hand-held butane gas canisters that have blown out windows without causing injuries. Messages left at the scene of some of those blasts have referred to small leftist or animal rights groups.

Mexico City chief prosecutor Miguel Mancera has described the blasts as the work of "some youth protest group." While the new manifesto was posted on a site that published radical animal-rights tracts, there was no immediate indication of other links to animal rights in the university blasts.

