Lethbridge police say they're investigating damage to the city's Pride crosswalk as a case of criminal mischief.

A substance that police initially described as "tar and manure" was dumped on the Lethbridge Pride crosswalk on Thursday but, after investigating further, police said it was actually black paint that had been strewn across the colourful street crossing.

What police at first believed to be manure turned out to be peat moss that had been used by an early-morning cleanup crew in an attempt to soak up the paint.

It was the second time this week that crosswalks meant to celebrate Lethbridge's LGBT community were damaged, as the city prepares for its ninth annual Pride Fest, which gets underway Friday.

Pride crosswalk vandalized Lethbridge

The above rainbow and transgender flag crosswalks in Lethbridge, Alta., were vandalized earlier this week. (Lethbridge Pride Fest)

"If this was something that was done deliberately to target Pride Fest and its members, it is incredibly disappointing to see a segment of our community treated with such disrespect," said Mayor Chris Spearman.

"Lethbridge is a welcoming, inclusive city, and the act of one or two ignorant people doesn't change that."

On Monday, visible tire skid marks were left on the rainbow flag crosswalk, as well as the transgender flag crosswalk.

The rainbow crosswalk has now been cleaned but will need to be repainted in time for the Pride Fest, which begins Friday and ends with a parade on June 24.