A Texas woman has been allowed to leave Mexico after being detained while trying to deliver Christmas gifts to a sprawling refugee camp housing people waiting in limbo at the border for US court dates to deal with their asylum claims.

Anamichelle Castellano said she and another volunteer for her not-for-profit group were stopped on Monday at a bridge crossing from Brownsville, Texas, to Matamoros, Mexico.

She said authorities discovered a small box of ammunition inside the car she was driving, which she said was left by her husband.

Mexico has strict laws against entering the country with guns or ammunition. Those laws occasionally ensnare Americans crossing the border.

Castellano said she spent Monday night sleeping on a couch with her nine-year-old daughter in a government office. She gave a statement on Tuesday to someone she believed to be a prosecutor, then was allowed to leave a few hours later. The prosecutor’s office in Mexico’s Tamaulipas state did not immediately respond to a request for comment on Wednesday.

Castellano and her husband, Jehu, operate a not-for-profit called the Socorro Foundation. They are among the volunteers trying to help thousands of parents and children waiting in Mexican border towns to seek asylum in American immigration courts.

Donald Trump’s administration has prevented many asylum seekers from entering the country or removed them from the US while their cases are still pending under a policy known as “Remain in Mexico”.

“Our faith is very strong,” said her father, Genaro López, on Wednesday. “God didn’t blink. He had a plan.”

Castellano said she and a group of volunteers had worked late into the night to wrap presents for children at the Matamoros camp, which consists of hundreds of tents pitched on the land next to the Rio Grande, the river separating the US and Mexico in Texas.

She said she had car trouble early on Monday and ended up driving her husband’s car. Her husband eventually took hers. They split about 300 gifts between the two.

While her husband drove into Matamoros without incident, an official told Castellano her vehicle would require extra screening. When she was told officers would unwrap all the gifts in her vehicle to check them for anything dangerous, she consented to the officers using an X-ray machine to examine the vehicle.

That scan uncovered a small box of ammunition, which she described as about the size of the palm of a hand. Castellano said she didn’t know about the box until the scan and had not intended to take it into Mexico.

She was told conflicting information during the two days about whether she could leave or if she would be imprisoned. She identified officers from at least three different agencies who asked her questions.

Ultimately, she was told that she and the other volunteer could leave if they paid $8,000. The fee was eventually lowered to about $4,000, and her husband paid $3,000.

She was told that she may have to return to see a judge in Reynosa, which she said she would do as soon as a court date was issued.

“I serve refugees,” she said. “To tell me that I can’t go back and give them their gifts and their needed supplies, I can’t risk that.”