(NewsNation) — The presence of Tren de Aragua gang members in San Antonio has raised alarms, especially among first responders who may be at risk while on the job.

San Antonio Professional Firefighters Association President Joe Jones sent a memo warning first responders to “keep your heads on a swivel and watch your six” for gang members, meaning to stay alert and watch their backs.

Several gang members were arrested Saturday in San Antonio during a multiagency raid on an apartment complex. People involved with the Venezuelan gang have been illegally entering the United States and have been arrested for committing crimes in various parts of the country.

How are police, firefighters responding to Tren de Aragua presence?

San Antonio Police Chief Bill McManus vowed to crack down on the gang’s presence in the south-central Texas city.

The firefighters union said higher-ups in the department began urging caution as the gang’s presence increased in certain parts of the city.

Jones worried gang members may confuse firefighter and paramedic uniforms for police uniforms, potentially putting first responders at risk of attack.

San Antonio firefighters are unarmed, and it’s common for them to take a police escort when entering hostile environments that could lead to violence.

There are currently no police escorts for firefighters in areas where there is a Tren de Aragua presence, but the San Antonio Professional Firefighters Association continues to push for better protective measures for their crews.

Tren de Aragua arrests in San Antonio

San Antonio authorities on Saturday cracked down on the gang’s presence at an apartment complex on the city’s north side, arresting four confirmed gang members.

It’s been less than three weeks since Texas Gov. Greg Abbott declared the gang a terrorist organization.

The raid, which included local, state, and federal authorities, saw multiple Tren de Aragua members arrested after complaints alleging human trafficking, narcotics violations and violent threats against building staff were made at the apartment complex.

According to police, 19 people were arrested: 16 Venezuelans and three U.S. citizens. Four were confirmed Tren de Aragua members and taken into custody by Homeland Security agents. Among those arrested, several of them had previously received deportation notices.