Four people are safe at home in California after being held in Russia for four days in a case that experts say is indicative of the strained ties between Russia and the United States.

Liana Randazzo, 27, Quygen Ngo, 24, Jennifer Phan, 21, and Sterling Winter, 18, had visited St. Petersburg in Russia to participate in a conference on international leadership for young people, but were suddenly taken away by Russian police and were informed they could face jail time before officials finally let them go, according to the San Jose Mercury-News.

Randazzo said they were “happy to be home” and that they “stood up for themselves” despite the Russians’ accusations. The paper quoted an expert as saying that the incident was likely a ploy by Russian leader Vladimir Putin to ruffle the feathers of the United States and prove his own power to his people, who are likely to be happy to see Americans “paid the price for a change.”

It was close to the end of the conference when Russian police demanded to see the group’s visas, and when they took the officials to their hotel rooms to show documentation, investigators suddenly began interrorgating the Americans. Later, they took them to immigraiton offices an hour away and continued their interrogation.

The U.S. State Department told the group that it was definitely not common for Russian officials to do this to visiting Americans, which highlights the tensions between the two nations.

The Russian investigators told the group their paperwork wasn’t complete, and they were using their tourist visas improperly. They appeared before a court that very night, and a judge continued it to the next day, forcing the group to stay in the country overnight. The judget told them he could choose to warn them, fine them, deport them, or even jail them.

Randazzo said the group was not too fearful because they knew the detention wasn’t about them, and that they were unlikely to be kept in Russia long term.

The group was represented by two lawyers who didn’t speak English.

In the end, the judge gave them fines of $100 each for improper documentation, and the group along with the U.S. State Department decided to leave immediately rather than stay the duration of the conference.