A MASSIVE explosion at an electricity substation on Tuesday night cut power to thousands of residents.

More than 3,000 people were without electricity from 11.30pm for up to three hours after a switchgear failure triggered a blast at the 11,000 volt substation in Sion Hill, Kidderminster.

Streets affected included Sion Hill, Stourbridge Road, Hurcott Road and Birmingham Road.

"A lot of people said they heard a very loud explosion," said firefighter Red Setter, who attended the scene in one of two engines from Kidderminster.

GPU Power UK said it was carrying out an investigation into the cause of the accident.