Santa Monica, CA - Authorities say an explosion outside a synagogue and Jewish school in Santa Monica was caused by a homemade explosive device and not an accident as previously believed.

Synagogues in California have been put on high alert after the bomb blast.

Jewish organizations around Los Angeles were urged to be extra vigilant after the explosion, which shattered windows at a synagogue and sent a 300-pound block of concrete flying into the roof of a nearby house.

Police spokesman Sgt. Jay Trisler said Friday that further forensic examination led investigators to conclude the blast that broke windows at Chabad House Lubavitch of Santa Monica on Thursday was intentional.

Trisler says police have linked the device to Ron Hirsch, a transient known to spend time at synagogues and Jewish community centers seeking charity.

Police are searching for Hirsch, whom they describe as "extremely dangerous."

The explosion sent a 300-pound pipe (136-kilogram) into a house where a child was sleeping and spurred police to evacuate several blocks, but no one was injured.

Investigators earlier said the blast was caused by an industrial accident. But "technicians and detectives conducted further forensic analysis at the scene and, after unearthing much of the large portion of the cement found, uncovered materials indicating that the device appeared to have been deliberately constructed," the FBI said in a statement. "Investigation has determined that items found in and around the mechanism are linked to an individual by the name of Ron Hirsch, identified as a transient."

Law enforcement sources told LA The Times that gun powder was among the items found in the explosive device. Officials have not said exactly how they linked the evidence inside the explosive device to the suspect.

A large hole is left in the roof of a home after police and firefighters removed a device from the roof of a home next to the Chabad House Lubavitch in Santa Monica, Calif., on Thursday, April 7, 2011. An early morning explosion sent the object into the air, lodging it in the roof. Concern that it was a bomb due to its proximity to the Chabad House Lubavitch caused authorities to evacuate about 100 people in the surrounding area. (AP Photo/David Zentz)Hirsch, 60, also known as Israel Fisher, is thought to be behind the blast on 17th Street between Broadway Street and Santa Monica Boulevard. Police described Hirsch as a transient.

"Hirsch should be considered extremely dangerous," said a police bulletin sent to other law enforcement agencies.

He is described as white, 5 feet, 7 inches tall, 207 pounds, with brown hair and green eyes.

The bulletin said Hirsch was known to frequent synagogues and Jewish community centers in search of charity, among them Congregation Bais Yehuda on North La Brea Avenue in Los Angeles.

The motive for the attack was unknown, police said. Joining local authorities in investigating the case were the FBI and the U.S. Bureau of Alcohol, Tobacco and Firearms.

On Friday afternoon, the Anti-Defamation League issued a security alert to synagogues and other Jewish organizations in the Los Angeles area.

Amanda Susskind, the league's Los Angeles regional director, said in an interview that the alert was "not intended to create panic or a drama," but rather to keep people on the outlook for a man who seems to be disturbed.

She also said there was no indication that the suspect was part of a terrorist plot.

"[The incident] seems more in the nature of a disturbed individual," she said.

"If he's out there and has nefarious goals, we wanted people to be extra vigilant and careful," she said.

Susskind also said she hadn't heard of Hirsch being seen at synagogues or community centers on Friday night, when Shabbat services were held. She added that "if there had been another incident, we would've heard about it."

During Shabbat, observant Jews are not allowed to use the telephone. But an exception was made Friday night, according to Susskind.

"We had indicated that this was worthy of breaking the rule," she said. "If anybody did see [Hirsch], we instructed them to call law enforcement directly."

Susskind said she isn't sure if he is Jewish.

"We're all wondering that," she said. "Both the name and alias are Jewish names, but I don't have any independent knowledge [if he is Jewish]."

Mirel Levitansky, who works at the Chabad House and is the wife of co-Rabbi Eli Levitansky, told Santa Monica Patch on Friday that Hirsch had stopped by the synagogue "over the years." She said she didn't interact with Hirsch when he visited the Chabad House.

"He makes his rounds, looking for handouts, for money," she said. "He hasn't caused any trouble [in the past]. He needs a little bit of help."

Hirsch is 60 years old, has brown hair and green eyes, is 5' 7" and weighs 207 pounds. Those with information about him are asked to call SMPD Det. Derek Leone at 310.458.8949.