A new national Amber Alert system officially rolled out earlier this month to millions of cellphones, and because the alerts are automatically active on most newer phones, the messages have already taken tens of thousands of people by surprise.

The newly-expanded emergency alert system is an effort by FEMA to update the way it reaches people with new technologies, but local officials and others worry that the lack of public education and some initial stumbles may undermine the program's purpose, especially when people are startled and annoyed and choose to opt out.

Lisa Rott was jolted from her sleep at 1:44 a.m. earlier this month in her Sarasota, Fla. home. A high-pitched tone sounded in spurts for about 10 seconds while her phone buzzed multiple times.

Initially Roth, 50, was worried something had happened to her elderly mother. Then she saw the message: "Emergency Alert: Amber Alert. An Amber Alert has been issued in your area. Please check local media."

"I thought it was spam," said Rott, who works for AT&T as a process engineer. And because her cellphone has a New Jersey number, she wasn't sure exactly where the alert originated. The next morning Rott searched online for both New Jersey and Florida incidents yielding one likely possibility — hours away from her home.

"What are we supposed to do?" Roth said. "They're not telling us what to do, they're not even telling us what to look for in our area."

Later that morning Rott called AT&T, her service provider, and asked them how to make the "worthless" messages stop.

Dozens of people have similarly taken to Facebook and Twitter to comment on being startled awake, scared by their phone's activity, and frustrated by the lack of information.

FEMA officials said they are aware of the confusion the Amber Alerts have caused and are working with the U.S. Department of Justice to include more information in the text messages.

"There's a very delicate balance between how much is enough and how much (alerting) is too much," said Damon Penn, who oversees the FEMA emergency alerts system. "The big concern is over-alerting, and that's what we're focused on."

The federal agency requires people sending the alerts to be trained and to ensure that the alerts meet specific criteria. But officials are still working on trying to determine whether an alert should be sent out in the middle of the night, what information to provide, and how best to use the system, Penn said. The agency has started an education campaign, he said.

"My biggest concern is that people, if they don't understand what it means ... will opt out of the program," said Bob Hoever, a director at the National Center for Missing & Exploited Children. "And it's critical that we continue to have their participation."

The organization activates the messages seen on billboards and now cellphones once officials tell them an Amber Alert is necessary. Since the program's inception in 1996, Hoever said Amber Alerts have helped officials safely return at least 602 children.

So far, 19 Amber Alerts have been issued under this new system in 14 states including Texas, Ohio, Colorado, Washington, Oregon, Pennsylvania and Arizona, according to figures kept by the National Center for Missing & Exploited Children.

While no Amber Alert has been issued in California under the new system, authorities say it's only a matter of time and people need to know it's going to happen.

"I know this is not our system, but we're going to be receiving the phone calls when this goes off," said California Highway Patrol Capt. Greg Ferrero, California's Amber Alert coordinator.

Ferrero said he's seen the stir caused by the alerts when they caught people off guard in Florida and Texas, where four have already been issued. He said FEMA needs to tell the public about the system, and has sent in suggestions to improve the program such as providing people with details like the license plate or where the abduction occurred.

Los Angeles Police Department Det. Kevin Coffey trained local law enforcement officers on the alerts last week and found most were surprised by the new reach they already have.

"We've never had this ability," Coffey said. "We're going to have instantaneous connectivity with every person with a cellphone within our county and potentially multiple counties in the state."

Timothy Griffin, a professor of criminal justice at University of Nevada, Reno has studied Amber Alerts for the last eight years. He said he favors an Amber Alert system that's more targeted, but his research also questions whether the system's effectiveness has been oversold.

"Amber Alerts, in most cases, make no difference whatsoever," Griffin said. "Even when you look at ones where Amber Alerts make a different, it doesn't happen fast, within that crucial three-hour difference" that the alerts are supposed to target. But he said he's hoping this system will prove him wrong.

Tami Abdollah can be reached at Twitter.