The devices used in two firebombings targeting UC Santa Cruz biologists are similar to some used in the past by animal rights activists, investigators said Sunday.

The bombs were so powerful they were like "Molotov cocktails on steroids," said Santa Cruz police Capt. Steve Clark.

One struck the home of assistant biology Professor David Feldheim on Saturday morning, forcing him to flee with his family. The other exploded just a few minutes earlier, gutting a car parked outside the campus home of a second researcher.

Later, Santa Cruz County sheriff's deputies went to the home of a third researcher who received a threatening telephone message, but officers found no explosives.

More than 50 investigators, including some from the FBI's regional terrorism task force, are looking into the attacks.

Feldheim, whose townhouse was firebombed just after 5:30 a.m., uses mice in laboratory research on brain formation.

He told The Chronicle that he and his wife, along with their 7-year-old son and 6-year-old daughter, had to drop a ladder from the window of a second-floor bedroom to escape after smoke filled the home's first floor.

"Everyone is OK," Feldheim said in an e-mail. "The kids are taking it pretty well. My wife and I are very shaken up. I also injured both feet in the escape."

Act of terrorism

Feldheim was treated at a hospital and released, police said. Clark said the attack on Feldheim is being considered an act of terrorism and attempted murder.

Clark said the bomb at Feldheim's house was similar to those used by animal rights extremists in the past, adding, "There are instructions on how to make it on their Web sites."

Feldheim and the unidentified faculty member who received the threatening message were named on pamphlets that were left on a stack of newspapers in a downtown Santa Cruz coffee shop last Tuesday, Clark said. The unsigned pamphlets at Caffe Pergolesi, which printed 13 researchers' pictures and addresses, called them murderers and torturers and said, "Animal abusers everywhere beware."

The name of the researcher whose car was bombed was not on the pamphlets, Clark said.

The attacks may mark an escalation in a series of protests against UC researchers that prompted a Los Angeles Superior Court judge to issue a temporary restraining order against three animal rights groups in February.

In January, a Molotov cocktail exploded on a UCLA researcher's porch. A month later, six people in masks tried to force their way into the home of a UC Santa Cruz researcher and hit her husband on the head, police said.

And at UC Berkeley, officials said 24 animal researchers and seven staffers have been harassed in recent months, with some homes and cars vandalized.

Clark said authorities are offering security to UC Santa Cruz animal researchers and have contacted every person named on the pamphlet, whether or not they were involved in animal testing. He said investigators were combing the Internet to see if anyone would take credit for the attacks. But as of Sunday, no one had.

"It's one thing to be an activist, it's another to be an extremist," Clark said. "It's absolutely outrageous that you would bring this kind of an attack to a family, all because of your passion over this cause. To me, it's indicative of people who have a complete inability to articulate their point in a constructive manner."

UC Santa Cruz Chancellor George Blumenthal condemned the bombings as "criminal acts of anti-science violence."

A different view was expressed today by Jerry Vlasak, a Los Angeles spokesman for the North American Animal Liberation Press Office, which often posts on its Web site communiques from activists taking credit for attacks. He said the benefit of animal research does not justify its expense or the exploitation of animals.

Vlasak said the bombers likely were not trying to hurt Feldheim, but were instead "trying to send a message to this guy, who won't listen to reason, that if he doesn't stop hurting animals, more drastic measures will be taken ... it's certainly not an initial tactic, but a tactic of last resort."

Feldheim, whose work includes introducing genes into living mouse brains, said Sunday that his research "is aimed at understanding how brain connections form during development, with special focus on the visual system." He said the work is important "so we can learn how to fix these connections after damage due to injury or disease."

Sunday afternoon, Feldheim's front door and concrete patio in a complex of townhouses on Village Circle remained blackened by flames and smoke. A neighbor said that residents, who are mostly faculty and students, awoke to the sound of an alarm.

"I feel bad that anyone would take that drastic a step to harm people," said Miriam Ting, a Santa Cruz pharmacist.

No answer

Just a few blocks away, no one answered the door at the brown faculty townhouse where the car had been firebombed, and a biology professor listed as living there did not respond to an e-mail. His driveway was still charred; the car was no longer there.

"It's a threat to everyone who lives here," said David Anthony, a history professor whose home is attached to the one where the car was firebombed.

Feldheim described a frightening escape. When the bomb exploded near his front door, he said, his family was awakened by the sound of smoke detectors.

"The downstairs was so smoky that we could not see," said Feldheim. "My wife and children all escaped out of the bedroom window using a fire-escape ladder. A neighbor and then the Fire Department came and put out the fire."

Feldheim said his home had been vandalized last year, with "hateful messages" written in chalk on the sidewalk outside, trash strewn about and some flower planters broken. The university responded by paying for an alarm system and motion-sensitive lights, he said.

"I'm not sure what we'll do in the future," Feldheim said.