MATAMOROS, Mexico (NewsNation) — Authorities in Mexico announced the arrest of five people on Friday in connection with an attack that left two Americans dead.

The suspects were arrested in connection with a kidnapping and homicide investigation, according to Tamaulipas Attorney General of Justice Dr. Irving Barrios Mojica.

It’s not clear if the suspects who were arrested were the men left handcuffed — purportedly by Gulf Cartel members — with an apology note for the killings.

Initial reports claimed the Americans were traveling down to the area for a medical procedure. But new information has raised questions about a possible connection between the Americans and the kidnapping.

Mexican law enforcement agents said they were investigating the possibility that members of a drug cartel kidnapped the Americans thinking they were encroaching on their turf, according to an internal government document seen by Reuters.

Mexican sources told NewsNation that the Gulf Cartel is in charge of the region and has turned Matamoros into part of a key drug trafficking route for the distribution of cocaine.

There has been a large, heavy police presence since the incident. Two men were arrested earlier Wednesday in Matamoros and brought in for questioning. It’s unknown if those arrests are connected to the kidnapping case.

Reuters contributed to this story.

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