Authorities in northwestern Wisconsin are tracking hundreds of tips and scrutinizing social media and phone records in a rapidly expanding search for a 13-year-old girl who has been missing since her parents were slain in the family's home outside Barron, Wis.

The Barron County Sheriff's Office believes Jayme Closs is in danger and has been since deputies responded to a 911 call shortly before 1 a.m. Monday. It was then that deputies found her parents shot to death in their home on wooded land set back from a highway west of the city of 3,300 residents.

In a morning news conference Tuesday, Sheriff Chris Fitzgerald discounted the notion that Jayme had run away and said she should be considered "missing and endangered."

The sheriff, when asked by a reporter when was the last time Jayme was seen, paused and gathered his thoughts before saying, "I believe [it was] Sunday afternoon. There was a family gathering … that she attended [not at the girl's home]."

That would be at least eight hours before the bodies of her parents — James Closs, 56, and Denise Closs, 46 — were found.

The FBI, state investigators and the National Center for Missing and Exploited Children are assisting Barron County in the search for the girl.

The national center said Monday afternoon that an Amber Alert had been issued in an effort to spread the word about Jayme's disappearance. The center's notice said the teen was taken from her home early Monday morning, "likely with a gun."

As of Tuesday afternoon, authorities had received more than 200 tips, Fitzgerald said. One came from as far away as Miami, Fla., and prompted police there to post late Monday on Twitter about a possible sighting of the teen earlier in the day.

Jayme "may have been seen in the afternoon of 10/15/18, in the area of NW. 27 Ave and 11 St.," the tweet said. "If it was her, she was in a black Ford Explorer with a possible WI plate of I60WER. If you have any information please call 911 immediately."

A check of the license plate on two public websites turned up nothing, but changing the letter "I" to the numeral "1" in online searches showed it belongs to a 2017 Ford Explorer.

"We have no credible information about the Miami incident," Fitzgerald said. Then he added: "I can't say that it was not her."

'Sweet and shy'

Fitzgerald said investigators, among the "well over 100 strong" working the case, are "questioning a lot of people" and revisited the Closs home "to make sure we didn't miss anything." He said "nothing new was found" at the home that would help in the search for the girl he described as a "sweet and shy 13-year-old who enjoys dancing and sports."

In one of two news conferences Tuesday to update the public on the case's status, Fitzgerald also shed more light on the 911 call from a cellphone in the home that brought deputies to the scene early Monday. He said there was some kind of disturbance that could be detected, but there "was no contact with somebody who was on the other [end of] the line. That's what was unusual about that 911 call. There was no one communicating with our dispatcher."

Fitzgerald said he has no information on how long the parents were dead before the bodies were discovered. He has said that "gunshots are involved," but didn't say whether gunfire killed them. Autopsy results are expected Wednesday.

Family members told CBS News in a telephone interview that the front door of the family's home was shot in.

Joining Fitzgerald at an afternoon media briefing at the Barron County Sheriff's Office was Barron Area School District Administrator Diane Tremblay, who said she knows Jayme as "a loyal friend" to her classmates at Riverview Middle School and who competed on the school's cross-country team.

Tremblay said a teacher recalled Jayme answering a question about what she would do with $1 million, and the girl answered, "Feed the hungry and give the rest to the poor."

The SUV spotted in Miami stopped at a Sunflex gas station, and video surveillance from the business with a 3:34 p.m. EDT time stamp was being reviewed by law enforcement, said officer Michael Vega, a Miami police spokesman.

A 39-second clip released by the gas station to a television station shows the SUV pulling up near gas pumps and what appears to be a slender young person with long hair moving about in the front passenger seat. One person then exits the back seat and speaks with the driver.

Vega said the tipster "believes that could have been this young lady in a Ford Explorer," and she was with two well-dressed men with beards, each 5 feet 7 to 5 feet 9 inches tall and weighing 250 pounds.

"We are getting the video from the gas station to see if it corroborates with what the tipster says," Vega added.

Vega said the tip initially came in an e-mail to a high-level member of the police department and that the source had been contacted by investigators Tuesday morning for more details.

Jayme is described as white, 5 feet tall, 100 pounds, with green eyes and blond or strawberry blond hair.

Anyone with information that could lead to her being found is urged to contact the Sheriff's Office at 715-537-3106 or 911.

"That's why this operation is running 24/7," Fitzgerald said. "We have teams standing by at a moment's notice when a tip comes in. … Every second counts in this case. … Jayme is out there. We want to find her. That's our goal."