(CNN) Samantha Taylor was at Orlando's Jewish Community Center for a morning meeting when she heard reports of a bomb threat crackle from the director's walkie-talkie.

Her daughter attends preschool there; she ran to the classroom and evacuated with the students and teachers.

While police and bomb-sniffing dogs searched the building for several hours, the teachers kept the children calm and happy at a safe spot down the street, Taylor said. No explosives were found.

On the same day, January 4, an Orlando Chabad center also received a threatening call, marking the first trickle in what would soon swell to waves of calls menacing Jewish institutions across the country.

In all, 48 JCCs in 26 states and one Canadian province received nearly 60 bomb threats during January, according to the JCCA, an association of JCCs. Most were made in rapid succession on three days: January 9, 18 and 31. A number of JCCs, including Orlando's, received multiple threats.

On February 20, another wave of bomb threats hit 11 JCCs across the country, bringing the total to 68 incidents targeting 53 JCCs, according to the JCCA.

That night, Ivanka Trump, who converted to Judaism, tweeted: "America is a nation built on the principle of religious tolerance. We must protect our houses of worship & religious centers. #JCC".

America is a nation built on the principle of religious tolerance. We must protect our houses of worship & religious centers. #JCC — Ivanka Trump (@IvankaTrump) February 20, 2017

Ivanka Trump was the first member of the Trump family to comment on the bomb threats. The next day, President Donald Trump himself denounced the JCC bomb threats and anti-Semitism.

"The anti-Semitic threats targeting our Jewish community and community centers are horrible and are painful and a very sad reminder of the work that still must be done to root out hate and prejudice and evil," Trump said after a tour of the National Museum of African American Museum and Culture.

In a statement, the FBI said the bureau and the Justice Department's Civil Rights Division are "investigating possible civil rights violations in connections with threats to Jewish Community Centers across the country."

The Simon Wiesenthal Center has urged Attorney General Jeff Sessions to appoint a special task force to catch the culprit, or culprits, behind the bomb threats.

"The multipronged threats of anti-Semitism today demand concerted action," said Rabbis Marvin Hier and Abraham Cooper, of the Simon Wiesenthal Center, a leading Jewish human rights organization.

The Council on American-Islamic Relations offered a $5,000 reward for information leading to the arrest and conviction of people behind the threats.

The JTA, a Jewish news agency, says it has obtained a recording of one of the calls . On it, the caller says a C-4 bomb has been placed in the JCC and that "a large number of Jews are going to be slaughtered."

JUST WATCHED More bomb threats, anti-Semitic vandalism in U.S. Replay More Videos ... MUST WATCH More bomb threats, anti-Semitic vandalism in U.S. 03:05

Several JCC sources said the FBI has told them it is investigating the calls as hate crimes. Online, another term has circulated: "telephone terrorism."

"I've been in the business for 20-plus years, and this is unprecedented," said Paul Goldenberg, national director of the Secure Community Network, which advises Jewish organizations on security. "It's more methodical than meets the eye."

No bombs have been found, but Jewish leaders hesitate to label the calls "hoaxes." The chaos and terror the calls have caused are real, as are more tangible consequences.

JCCs across the country are bolstering security and holding town halls to calm frightened parents. Still, several centers have seen students withdraw from their early childhood education programs, typically reliable sources of revenue. As a result, some are slashing budgets, cutting staff and holding emergency fundraisers.

In Orlando's JCC, 50 students have been withdrawn from its day care and preschool. In Albany, New York, 12 families have removed their children.

"If we happen to be on the list again," said Adam Chaskin, director of Albany's JCC, "that number 12 is going to grow."

Some parents wondered why the threats had not garnered more media attention and lamented the spike in hate crimes seemingly incited by the divisive 2016 presidential campaign.

Others have agonized about whether to withdraw their children from JCC schools and cringed when they hear a text message alert on their phones.

"Everywhere I went I had my phone out front and center," said Taylor, a 37-year-old mother of three. "It was like: OK, when is it going to happen again?"

A community on edge

Like YMCAs, Jewish Community Centers pride themselves on being open to all members of all faiths, and a fair number of their students are not Jewish.

But for many Jews, JCCs aren't just about schools and swimming lessons. They're hubs of Jewish social life: places where their children learn Jewish history, their families celebrate Purim parties, and one of the few spots where Jews of all denominations put aside their religious and political differences.

"So much of being Jewish is built around community," said Jordana Horn, a mother of six in New Jersey whose children and parents both frequent the local JCC. "Everything from prayer to mourning to celebration you need to have a community around you. You need to have a place where everyone can gather."

For secular Jews, the JCC may be one of the few institutional sources of knowledge about Jewish culture and tradition.

Daniel Mauser and Kristina Kasper, who live in San Diego with their two children, don't belong to a local synagogue but send their son to a JCC preschool. It's the best in the area, they said.

Still, they know that the school, which received a bomb threat on January 31, comes with risks.

"Even though it's a wonderful environment, I know that, in sending my son to a Jewish preschool, it's a target," said Kasper, a former New York City schoolteacher.

Not all of the threats against JCCs in recent memory have been empty.

In 2014, a white supremacist murdered two people outside a Jewish Community Center in Overland Park, Kansas. In 2006, a man fired shots at the Jewish Federation of Seattle, killing one woman and injuring five others. Five years before that, another man opened fire at the JCC in Granada Hills, California, wounding five people, including a 5-year-old boy.

In 2014 and 2015 the FBI tallied more than 1,270 hate crime incidents targeting Jews, far more than any other religious groups, and some Jewish leaders say the situation is getting worse.

In the past several months, synagogues and schools have been vandalized, swastikas have been scrawled in New York City subway cars and Jewish families have been harassed by neo-Nazis.

"We are in a volatile and fast-growing threat environment," said Jonathan Greenblatt of the Anti-Defamation League. "The Jewish community has been on edge."

Little is known about the calls themselves. Goldenberg, the security adviser, says the caller uses sophisticated voice-masking technology. It's difficult to discern if it's a male or female voice, or how old the caller is.

"They could be 15 or 60 years old. These masking technologies are very effective."

Chillingly, the perpetrator also uses technology to make the calls seem as if they're coming from within the JCC itself.

'How serious is it?'

The photo of the worried woman pushing an evacuation crib outside the Albany JCC -- that's the image that roiled Kveller.com's Facebook group for mothers, said Deborah Kolben, editor of the Jewish parenting website.

Jewish Community Center evacuation

Since the threats began, Kveller has run at least five columns about them. Some of the writers are distraught. "Did the people who decided to call in a bomb threat wish it was real?" asked one mother . "Did they think about my babies and wish that they could really blow them up?"

Others columnists were more defiant. "I'm not scared to be a proud Jewish mother in the United States of America in 2017," wrote Jordana Horn , "and neither should you be."

Other Jewish mothers say they don't know what to make of the bomb threats, or how they should react.

"The question is: How serious is it?" said Elissa Strauss, a parenting columnist for Slate whose son attends a JCC preschool. "That's what I, as a Jew and a parent, am trying to work out. I don't think I have a clear understanding of what I'm supposed to do right now, besides not give in."

Strauss said the relative lack of media coverage about the threats adds to her perplexity. She's not alone: "48 U.S. Jewish Centers Received Bomb Threats in Past Month," ran a headline in Haaretz. "'Why Is No One Talking About This?'"

Parents are asking: Is it because no bombs have exploded? Because the protection of children is seen primarily as a "women's issue"? Because Trump's chaotic new administration dominates news cycles? Or because JCC leaders are trying to quiet the story for fear of panicking parents and losing students?

Ivy Harlev, director of the JCC in Wilmington, Delaware, which received two bomb threats last month, says she is "torn" about whether more media should have covered the threats.

"I don't want that kind of negative attention, but I want to make sure that people know that we are a secure place, and that we have the support of local law enforcement."

Like many JCCs that have received threats, Harlev's quickly assembled a town hall so parents could question administrators, local police and FBI representatives. Two families decided to withdraw their children from the JCC's early childhood education program, Harlev said.

In Albany, Orlando and elsewhere, JCC staffers have tried to bolster security -- and ease parents' peace of mind -- by closing entrances, blocking phone calls from unknown numbers and posting bollards to block vehicles from getting close to their buildings.

At least one family was satisfied by the changes.

For nearly four years, Melissa Braillard, a mother of two in Orlando, had sent her children to the JCC. She knew and liked the teachers, the administrators, the other parents and their children.

"I feel like I had a support system, and people cared for us."

But after the third bomb threat and weeks of worrying, Braillard removed her children from the JCC. "I need to keep my kids safe," she thought at the time.

A few weeks later, though, Braillard agreed to return to the Orlando JCC to see its security improvements. She came away impressed.

Because her son would be starting kindergarten soon at another school anyway, he is not returning to the JCC. But Braillard planned to re-enroll her daughter.

On March 8, the Orlando JCC is holding a fundraiser , where it hopes to raise $200,000 to help the center break even for the year. It has already found three donors to match donations, potentially quadrupling the windfall.

Meanwhile, parents like Taylor, the mother who witnessed the first bomb threat, are determined to keep the doors open. "Our JCC isn't going anywhere," she said, "and that's the most important message."