Council chiefs have slammed pranksters who caused foam to fill a popular water feature in South Tyneside - and said fountain will be out action for some time.
Giant peaks of froth formed in the artificial waterfall in South Marine Park in South Shields last night, with chunks of foam floating off onto nearby roads.
Bosses at South Tyneside Council have launched an investigation into the foam, but suspect it was a "stunt" and say such incidents can cause damage to the water feature and risk harming wildlife.
In past decades, pouring washing-up liquid and other soapy substances was a common prank in the town. Water features outside South Shields Town Hall were often victim to such acts in the 1980s and 1990s.
A council spokesman said: "This irresponsible behaviour simply puts an additional burden on taxpayers who ultimately have to pay for this to be remedied.
"The waterfall will be out of action for some time."
The council said the foam incident came to the authority's attention via Facebook, and both a clean-up operation and an investigation into the source of the foam were now underway.
"We will be reviewing CCTV footage as part of our investigations," said a spokesman.
"Our maintenance engineers will drain and refill the water feature to try to address the problem.
"This sort of activity may seem like a bit of fun but it is important to note that it can be detrimental to fauna and flora as well as local wildlife. This type of stunt can also block the waterfall filters and damage the equipment used to make the waterfall an attractive place to visit."
Park visitors said the foam had first been spotted late yesterday, and suspect a soapy substance was poured into the fountain's pool last night, with the force of the falling water causing it to form giant mounds of froth.
One man said: "I was coming up Sea View Terrace when I saw foam floating in the air, and then a huge chunk of it sitting in the road.
"I thought 'hang on?' and knew it must be coming from the fountain in the park. When I went round it was full of foam."