“We will not hesitate to carry out our actions against the system of domination and against those who support and protect it,” it read.

A manifesto posted on the radical website mentions at least five other Mexican researchers whose work it opposes.

The attorney general warned universities, businesses, and professional groups involved in nanotechnology to beef up their security and notify authorities of anything suspicious.

The attacks already have spurred some universities to take extra security precautions.

Officials at the campus hit by the 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 Aug. 9 at a Mexico City research institute, but an institute spokeswoman later told local media the package simply contained books.

In a statement, the head of Mexico’s National Association of Universities, Rafael Lopez Castanares, condemned the attack.

“I would link [these attacks] to some type of imbalance totally foreign to the causes of universities,” he wrote.