Dogs in the City
Comedian Justin Silver hosts "Dogs in the City." CBS

The mayor's office in Colmenar Viejo, Spain has hired a detective to catch owners who fail to pick up their pet's excreta, say officials.

Colmenar Viejo, a historical town north of Madrid, said fines and warning signs have proved to be not enough for pets' owners who still fail to pick up the animals' faeces.

The town's mayor has therefore decided to hire a professional 'Canine Detective' who will spy on dog-walkers, IOL News reported.

"This person, incognito, will watch the streets and public spaces in which most dog dirt has to be cleaned up," an official announcement said.

"Their job will be to film owners who do not pick up after their dogs in flagrante and hand in this evidence along with a report as proof in police proceedings," the statement continued.

It hasn't been confirmed whether the actual dog mess will be collected as further DNA evidence of the misdemeanour.

The town hall added that offenders would face possible fines of up to 150 euros (£123), with higher penalties for repeat offenders.

Before the detective starts work, authorities have sent actors into the streets dressed up as detectives to warn locals of the anti-excrement campaign, which it said was motivated by health concerns.

"Most dog owners are responsible people who do not let their pets defecate in inappropriate places and pick up the excrement immediately," said Colmenar Viejo's conservative Mayor Miguel Angel Santamaria.

"But unfortunately there is a minority that lacks consideration for others and leaves a trace of its incivility in streets, pavements and even the entries to schools or children's playgrounds."

Colmenar Viejo is one of dozens of Spanish towns and cities cracking down on negligent pet owners, the Guardian said.

In Barcelona and Madrid, offenders risk fine up of up to €1,500 (£1,239).

In the outskirts of Madrid, the municipalities of Alcalá de Henares and Leganés have undercover police who watch pet owners, while in Móstoles, the task is carried out by neighbourhood volunteers.