The incident happened around 11pm at the Dallas Group of America in the 300 block of Dock Road.
Texas City's emergency manager Bruce Clawson says there was a hydrochloric acid leak from a tank in the port area and it created a cloud that began traveling over the city, prompting officials to issue a Level 3 shelter-in-place. People were advised to stay inside, turn off air conditioning and keep windows and doors closed.
City officials lifted the citywide lockdown just after 5am. Access to several roads in the south part of the city were closed for hours but have since reopened.
"A couple of firefighters were exposed and there were a number of workers, 4 or 5. They were all transported to the hospital to be checked out," Clawson said.
We're told their conditions are not life-threatening.
Officials say they will be in clean up phase for the next several days. There were no evacuations issued for nearby residents.
Hydrochloric acid is a widely used strong corrosive irritating acid that is normally present in dilute form in gastric juice.
According to the city's emergency management website, a Level 3 emergency means:
"An incident has occurred the situation is not under control and protective action may be necessary for the surrounding or offsite area. Additional IMAS aid may be needed. The EOC is activated, the Siren warning is given to the Public, Channel 16 and Radio Station 530 AM are constantly updated informing the Public of the status of the incident. You may also want to use any major television station in the Houston area for updates. The situation is often fluid and up-to-date information can be obtained by using these stations as they often have live broadcasts of the event."
According to the website, any time sirens are sounded, residents should go indoors, shut all windows and doors and turn off the air conditioning.
The Dallas Group is a producer of adsorbent synthetic magnesium silicate and the only North American-based manufacturer of ammonium chloride, according to the company's website.
People were advised to stay inside, turn off air conditioning and keep windows and doors closed.