Fire trucks from Minneapolis and four suburbs rushed to the main building of the Minneapolis water treatment plant in Columbia Heights Tuesday afternoon after two chemicals were accidentally mixed.The building was evacuated but there were no injuries, said John Larkin, assistant fire chief for Columbia Heights. He said the public was not in danger.

"Minneapolis tap water is safe to drink," the city of Minneapolis said in a later afternoon news release, adding, "drinking w ater was never at risk of contamination."

Larkin said his department received a call at 1:09 p.m. when a duct detector alarm went off, that is usually activated by heat or smoke. "When we got here, we met with staff," Larkin said. He said treatment plant employees had accidentally mixed together 6,000 gallons of hydrochloric acid and 500 gallons of caustic soda, which he said can generate excessive heat. The sprinkler system was activated, Larkin said, but it was unclear whether it was heat from the mixture that set it off.

About four or five workers in the plant were evacuated and the Minneapolis hazardous materials team went into the plant to assess the situation, he said. The city said in its news release that the crews determined the building was safe, and was reopened to employees. Columbia Heights sent four fire trucks to the scene, Minneapolis sent at least a half dozen, and trucks also came from St. Anthony, Fridley and Brooklyn Center, he said.