Police arrested 42 people and seized more than five tons of hashish with the help of information received via Twitter. ALEJANDRO GARCÍA / EFE

What started as a campaign asking for the public’s help on Twitter has grown to become one of the most effective methods for cracking down on drug traffickers in Spain, with more than 800 arrests in the past two-and-a-half years.

Spain’s National Police has gone from putting up wanted posters for traffickers to searching for them with help from the social networks using the hashtag #tweetredada (tweetraid).

The Spanish National Police has more than 1.66 million followers on Twitter

The tag allows anyone to tip off authorities about drug transactions – regardless of whether they are large or small – taking place throughout the country.

The police have also set up a separate email account, antidroga@police.es, for the same purpose, and are urging people to use it to “work together against the traffickers.”

#Tweetredada #verano: por unas playas limpias... de DROGAS. COLABORA contra los traficantes en antidroga@policia.es pic.twitter.com/58QQ7rCfNn — Policía Nacional (@policia) August 10, 2013

No one likes a squealer and, even worse, no one wants to face retaliation for passing on information about criminal activities. But the police’s new game plan has worked because citizens do not have to identify themselves when they write in, and all the information received is treated confidentially.

Once a tip is received, a group of officers at the Central Narcotics Unit will determine whether or not the information needs further investigation.

The approach began in January 2012. Two-and-a-half years and more than 35,000 messages laters, the National Police have more than 1.66 million followers on Twitter.

And the tip-offs continue to pour in.

For example on Wednesday, authorities reported the arrests of 42 members of an alleged drug-trafficking gang that was operating out of Barcelona and Cádiz. “Gang of drug traffickers broken up and 5,000 kg hashish and 27 cars seized in Barcelona and Cádiz....,” the police tweeted.

Desmantelada una banda de narcos e incautados en #Barcelona y Cádiz 5.000 kg de hachís, 27 coches... ¡Molt gràçies, crack! #tweetredada — Policía Nacional (@policia) July 8, 2015

During the course of the investigation, which began in April 2013, the police said they received numerous anonymous tip-offs “of vital importance” that led to the arrests.

The tweet about the arrested traffickers ends with a final message from the National Police giving their thanks in Catalan: “¡Molt gràçies!”