SAN DIEGO -- An immigration sweep that resulted in the arrests of dozens of illegal immigrants took place in the most unexpected of places, and immigration rights activists are unhappy with the operation, 10News reported.

The sweep, which happened Wednesday at the Old Town transit center, involved agents from the Transportation Security Administration and the Border Patrol.

The agents got on board a trolley and arrested 21 illegal immigrants, including three teenagers on their way to school. Those teens have since been deported.

Pedro Rios of the American Friends Service Committee said, "Some of them don't have any relatives in Mexico; they don't have anywhere to go."

On Friday, immigrant rights activists denounced the sweep and said the agents crossed the line and accused them of profiling.

"What gives them the authority to question only Latinos or people that looked a certain way?" said Rios.

The activists also questioned the Obama administration, wondering if this was the change in immigrant rights they thought was coming.

"This is a policy that violates human rights," said Rios.

A Border Patrol spokesman denied the use of racial profiling. He said behavior detection officers helped identify suspected illegal immigrants on board the trolley.

The spokesman said of the 21 detained, one person had a warrant out for his arrest and another had a felony conviction on his record.

Rios said he isn't buying that explanation.

"That's wrong, and it cannot be tolerated," said Rios.

Rios would not comment on the teens' legal status to be in the U.S. or the status of their families. He said a raid on public transportation would discourage other teenagers from going to school or adults from going to work.

There is no word on what happened to the other 18 people arrested in the sweep.

The three teenagers are currently in a shelter in Mexico, 10News learned.

While some questioned the legality of conducting a sweep on a trolley, a TSA representative said they have conducted more than 1,000 similar sweeps on a variety of modes of transportation, and federal law said it is legal.