Police officials in London have warned people who use Grindr of an alarming string of robberies associated with the hookup app.

Between December 31 and January 9, four men were drugged and robbed by two men who Metropolitan Police officials say they met on Grindr.

The victims reported agreeing to meet up with individuals from the app but that they became unconscious during the encounter and woke up realizing they had been robbed of their belongings, according to a Metropolitan Police statement.

The drugs did not cause lasting damage to the victims, but the suspects were able to flee the country, police officials said.

Now London detectives are appealing to the public and asking anyone with information or who may have been a victim themselves to reach out.

“We believe other victims may have been targeted,” detective superintendent Dan O’Sullivan said.

“However, for personal reasons, [they] may not have wanted to report it. If you have been a victim, you can report in confidence to us or speak to an officer from the LGBTQ+ community.”

Before meeting up with people they met on Grindr, users are advised to consider their safety. Police officials recommend telling a trusted person about one’s arrangements, watching one’s drinks for signs of tampering, and removing valuables from sight.

One should also verify the identity of somebody one may meet up with by insisting on getting video or photo proof that the person is who their profile photo claims they are.

Other tips include using messaging apps instead of social media accounts to communicate for added security and using reverse image search tools to check on the authenticity of any photos a potential connection sends.

“Although the suspects have fled the country and the risk to the community is reduced, we are continuing to engage with our partners and those from LGBT independent advisory groups,” O’Sullivan said.