FALL RIVER, Mass. (AP) – A police officer suffered minor chemical burns after a tanker carrying sodium hydroxide began spewing between 50 and 100 gallons of the liquid into the air.

The officer, whom a police spokeswoman would not identify, was treated for burns at St. Anne’s Hospital and released, The Herald News of Fall River reported.

The officer was responding to a false report of terrorism at EC Pigments on Quequechan Street. Police spokeswoman Lisa Ahaesy said the tanker driver called police, fearing he was being followed by terrorists.

In fact, he was being followed by members of the Teamsters Local 251 union, who were protesting tanker owner Univar USA’s use of non-union drivers, she said.

Three officers were talking to the protesters and a fourth was interviewing the tanker driver when the chemical began spewing out of the tanker and hit one of the officers.

Fire Chief Stephen Pietruska said the truck driver incorrectly replaced the cover on the tanker after getting a sample of the chemical before unloading it.

Univar did not return calls for comment by The Herald News.

Ahaesy said the Massachusetts Department of Environmental Protection is investigating the incident.

AP-ES-03-19-04 2012EST