Illegal dumping of animal waste into the sewerage system has clogged the Gozo sewage treatment plant, forcing its shut-down, the Water Services Corporation said on Thursday.
It said expensive equipment had been severely damaged at the plant, which supplies treated water to farmers.
Operations are expected to resume on Friday.
The corporation said it was collecting the necessary information to be handed to the police.
"The sewage infrastructure is very complex and delicate and it is damaged by improper use of the urban sewer system.
"It is therefore very important that only human toilet waste and degradable toilet paper are discharged in the system," it said in a statement.
Any suspected foul play or problems with the sewer can be reported to the corporation on 8007 6400, customercare@wsc.com.mt, through live chat at www.wsc.com.mt or on social media.
MEP Roberta Metsola had flagged the problem to the European Commission last month.