An 18-year-old woman suspected of making threats to Denver-area schools has been found dead in an apparent suicide, according to police.

Sol Pais was reportedly obsessed with the 1999 Columbine high school massacre, in which two teenagers murdered 12 students and a teacher.

The alleged threat led to school closures, affecting more than 400,000 students, and a manhunt for the woman.

She flew to Denver ahead of the 20th anniversary of the Columbine shooting.

Jefferson County Sheriff Jeff Shrader told reporters on Wednesday that she died from an apparent self-inflicted gunshot wound.

The FBI earlier tweeted there was no longer a threat to the community and the suspect is deceased.

Officials said at a news conference that local schools would reopen on Thursday and events marking the anniversary of the 1999 shooting would continue on Saturday.

The Miami Beach high school student travelled to Denver from Miami on Monday night and purchased a pump-action shotgun and ammunition, the Jefferson County Sheriff’s Office said.

At a second news conference later on Wednesday, FBI Denver special agent in charge Dean Phillips said that “a combination of her actions and comments” alerted authorities to Pais as a possible threat.

Mr Phillips said that Pais made comments in person and online related to her “infatuation” with Columbine. And she had purchased three one-way tickets to Denver from Miami for 15, 16 and 17 April, before taking the first flight on Monday. Mr Phillips said Pais went directly to purchase the weapon after landing.

Authorities are now conducting an investigation to ensure Pais had no accomplices and that there is no further threat.

“You should feel confident that your law enforcement community is protecting you and keeping you safe,” Mr Phillips said.

Police had considered her armed and extremely dangerous.

Nearly 30 armed officers swarm the woods near the Echo Park Campground in the Arapaho National Forest, CBS News reports.

The Echo Lake Lodge, nearby to where she was reportedly found, does not open until late May due to weather.

Witnesses told local media that she was seen running naked and armed with a gun in the area earlier on Wednesday. She had last been spotted in the Mt Evans area dropped off by a “for-rent vehicle”, Mr Phillips said.

A tragedy that cuts deep

Nada Tawfik, BBC News, Denver

Anniversaries can be difficult for survivors and the wider community, often triggering traumatic memories.

Littleton was already on high alert because they’ve faced threats in the past, and this was another scary reminder that the mass shooting will perhaps forever affect life in this city. One Columbine survivor told me that when she heard the news, she questioned her safety and took a different route home in a moment of panic.

Today, schools are closed, empty, and deemed unsafe. John McDonald is in charge of security for the school district that includes Columbine. He told me he was angry that as a country, Americans had done nothing but point fingers for the last 20 years, and as a result children weren’t just dead, they were unsafe to attend school.

Columbine isn’t even among the 10 deadliest mass shootings in this country any more. Yet, it is still a tragedy that cuts deep and becomes more painful with each reminder that nothing has changed.

The suspect’s family had urged her to turn herself in as authorities launched a manhunt.

• US schools close as armed woman hunted

“It’s like a bad dream. We don’t know. We don’t have any ideas,” her father told CBS News in Miami.

Mr Phillips declined to answer questions related to Pais’ mental health.

According to the news outlet, more than 130 schools in and around Denver had closed as officials searched for her.

At the news conference Tuesday afternoon, Mr Phillips said there had been information about a specifically targeted school.

Asked about a possible “overreach” in keeping so many students home from school Mr Phillips responded, “As a parent I would say thank you to the school system for protecting my child.”