Residents spoke of their shock as the River Irwell running through Rossendale began to run orange today.

The occurrence is not uncommon in Bacup and is a reminder of the area's industrial history, but this is the first time it has been recorded in almost five years and took many by surprise.

Mine water from the former Old Meadows Colliery, off Burnley Road, Broadclough, was last worked on in the 1970s and the iron affected 24km of the nearby riverbeds.

At the turn of the century a major engineering scheme had been devised which aimed at clearing up the river with a new multi-million-pound facility introduced to deal with the fourth highest levels of water pollution nationally.

After periods of wet weather or shift underground in the old mine means that the facility is swamped and reed beds are unable to deal with the increase in sediment flowing over them.

The treatment facility deals with 600 mega litres of water per annum and removes around 15 tonnes of iron particles every year before clean water is discharged.

James Deane, who moved to Bacup after the last incident, could not believe his eyes when he saw the coloured water flowing through the town centre.

He said: “It is the first time I have seen it. I was obviously shocked. It isn’t natural at all!”

One local wrote on Facebook: “Tomato soup comes to mind”

Another added: “Stop panicking. It will clear itself, it’s only iron in the water caused by some shift underground in the old mind forcing more than the reed beds can cope with.”

A spokesperson from the coal authority said: “We have been monitoring the source of the discolouration of the River Irwell in Bacup and can report that the water quality has improved overnight and continues to do so. 

"As has happened before in this area, recent rainfall caused a temporary increase in water flowing from mine workings in the area.  Our contractors will remain in the area until we are satisfied that the situation has returned to normal.”