WASHINGTON — The father and boyfriend of a missing teacher from Montgomery County tearfully pleaded with the pregnant 31-year-old to contact them and let them know that she is safe.

“All we want is her to come back to us,” the missing woman’s father Mark Wallen said. “Laura, if you’re out there listening, pick up the phone.”

Family members last heard from Laura Wallen on Sept. 4 when they received a text message from her phone. Police found her black Ford Escape several days later at an apartment complex in Howard County.

Detectives don’t know yet what led to Wallen’s disappearance and are treating the case as a missing person investigation.

She did not show up for the first day of classes at Wilde Lake High School in Columbia after spending two weeks preparing her classroom. She did not request a substitute teacher for that first day, which worried her family, her father Mark Wallen said Monday.

Wallen said his daughter is dedicated to her students and her work as a teacher.

“That was one thing that she had joy in her heart about,” he said.

The family is offering a $25,000 reward for any information that “would bring us back to her.”

Tyler Tessier, Laura Wallen’s boyfriend and the father of her baby, said they had attended doctor appointments together and that she had spoken to her co-workers about her pregnancy and how excited she was.

“It doesn’t matter what’s happened, it doesn’t matter what type of trouble, there’s nothing we can’t fix together,” Tessier said. “There’s so many people that miss you … we haven’t slept, we haven’t eaten, we’re just looking … we’re praying that you’re safe. I’m asking to just let us know that you’re safe.”

“If somebody has her, please understand you’ve taken away a huge person in so many people’s lives — her friends and family, students that she has. I know what she means to me, I know what she means to everybody else,” he said. “We just want her back.”

Police don’t know how Wallen’s car ended up at the apartment complex in Columbia, Maryland, and they don’t know if she knew someone who lives there, said Lt. Sean Gagen.

Police combed her car and her apartment for any clue of what might have befallen Wallen or where she might have gone. They sought subpoenas to search her computer, track her last known locations and determine whom she may have had contact with, Gagen said.

Gagen asked anyone who might have seen her over the Labor Day weekend or might know where they can find her to call police at 301-279-8000.

Wallen is described as a white woman with blond hair and blue eyes. She is about 5-foot-5 and weighs about 200 pounds. She is four months pregnant and had been driving a black Ford Escape with Maryland tags M522473.