WEST, Texas (AP) - The mayor of West, Texas, says volunteer firefighters went to fight a fire at a fertiliser plant about a half-hour before a massive explosion tore through it and damaged surrounding buildings.

Mayor Tommy Muska says he's a volunteer firefighter himself and his helmet was knocked off when the explosion tore through the West Fertiliser plant around 7 pm local time on Wednesday.

Mr Muska says the blast badly damaged buildings for a five-block radius around the plant, including a nearby middle school and nursing home. He says the nursing home's 133 residents were safely evacuated.

A Waco hospital official says at least 66 people were taken there for treatment, including some who were seriously hurt.