METAMORA, Ohio — A private donor has offered a $25,000 reward for information about the disappearance of 20-year-old Sierah Joughin, whose bike was found in a cornfield on a Fulton County road this week.

Authorities also have put out an alert to talk to a jogger who may have seen her before she was reported missing on Tuesday night.

The Fulton County Sheriff’s Office said Ms. Joughin, of Metamora, was last seen at 6:45 p.m. Tuesday on a purple bicycle in the Evergreen School District area. The bike was later found on County Road 6 around midnight, about an hour after Ms. Joughin’s mother called to file a missing person report, Sheriff Roy Miller said.

PHOTO GALLERY: Search for 20-year-old Sierah Joughin

Officials observed some type of disturbance around the bike, which was three to four rows deep into the cornfield, Sheriff Miller said. The corn around the bike had been trampled.

Today, volunteers are gathering to conduct a search for Ms. Joughin. The search area is being expanded to a four-square-mile radius. Authorities are asking anyone who has security systems or cameras to check those too for any suspicious footage.

On afternoon, the intersection of County Road T and County Road 6 remained blocked by the state highway patrol, restricting travel northbound on County Road 6 past the cornfield where the bike was found.

Less than a mile north, outside the homes of Ms. Joughin’s mother and grandparents, more than 100 volunteers had gathered by State Rt. 120, stopping cars and handing out flyers.

Ms. Joughin’s aunt, Carrie Joughin, said she did not know why her caring and compassionate niece had disappeared.

“That’s what is hurtful,” she said. “You want one good solid answer.”

Ms. Joughin has attended University of Toledo since the fall of 2014. She is entering her junior year and studying human resource management, according to the university.

“The thoughts and prayers of the UT community go out to her family and friends as authorities search to find her,” said Kaye Patten, senior vice president for student affairs, in a written statement.

Ms. Joughin, who family say has no enemies, is also working as a summer intern for a company her that uncle, Howard Ice, owns.

“She’s a very stable person,” Mr. Ice said, adding that the disappearance was “highly uncharacteristic” of her.

Ms. Joughin was apparently on her way back home from visiting her boyfriend, the sheriff said.

Given the suspicious nature of the disappearance, the FBI has gotten involved at Fulton County’s request. FBI special agent and Toledo supervisor Jake Hardie and his office is working alongside other agencies.

Officials already have used a specialized search dog from the Columbus area to scour the area.

After the sheriff’s office found the bike early Wednesday morning, it contacted the state for help. Using a helicopter with infrared vision, officials searched the area before contacting the FBI and other agencies at daylight that day.

As of today, no persons of interest had been named.

“I’m optimistic that we’ll find her with all the help,” Sheriff Miller said. “There are a lot of people involved, a lot of prayers being said.”

Ms. Joughin is white, about 5 feet and 5 inches tall, with brown hair and brown eyes. She was wearing shorts and a neon-yellow tank top.

Anyone with information is asked to call the sheriff’s office at 419-335-4010, ext. 8.

Contact Michelle Liu at mliu@theblade.com or on Twitter @mchelleliu.

First Published July 21, 2016, 4:00 a.m.