Plans by the hacker collective Anonymous to expose collaborators with Mexico's bloody Zetas drug cartel – a project it dubbed "#OpCartel" – have fallen into disarray, with some retreating from the idea of confronting the killers while others say that the kidnap of an Anonymous hacker, the incident meant to have spawned the scheme, never happened.

The apparent climbdown by the group came as one security company, Stratfor, claimed that the cartel was hiring its own security experts to track the hackers down – which could have resulted in "abduction, injury and death" for anyone it traced.

Two hacker members of "Operation Cartel", which said earlier this week that it would expose members of the murderous cartel, have now indicated that they are stopping their scheme to identify collaborators and members because they don't want anyone to be killed as a result.

Stratfor had warned on 28 October that there could be disastrous results from the plan: "Loss of life will be a certain consequence if Anonymous releases the identities of individuals cooperating with cartels. The validity of the information Anonymous has threatened to reveal is uncertain, as it might not have been vetted. This could pose an indiscriminate danger to individuals mentioned in whatever Anonymous decides to release."

The threat from the cartel had already worried some Anonymous members. The collective has no formal organisational structure; it exists through hundreds of members who communicate through chatrooms. Plans for attacks tend to float up through the discussions in the chatrooms, and can be carried out by a few or a few thousand participants, depending on the support ideas receive.

Thus there was widespread support among participants for "Operation Payback", a series of attacks on PayPal, Mastercard and Amazon earlier this year after they blocked financing for – or, in Amazon's case ceased, hosting of – the Wikileaks website.

But it is unclear how widespread support is within Anonymous for the original plan to expose "collaborators" – allegedly including police, taxi drivers and journalists – who work with the Zetas.

The Zetas have shown that they can be ruthless if information about them is posted online: in September, police in the Mexican border city of Nuevo Laredo found a woman's decapitated body alongside a handwritten sign saying she was killed in retaliation for postings on a social networking site. The message was signed with a "Z," the Zetas' trademark.

Earlier that month, the bodies of a man and a woman were found hanging from an overpass in Nuevo Laredo with a message threatening, "this is what will happen" to troublemaking internet users.

Some tweeters using the threat's #OpCartel hashtag said the whole idea is too dangerous to carry out.

"He denounced the op after safety concerns. He thought about it and saw it was too dangerous," posted a tweeter under the name GeneralSec. "DragnDon" tweeted back: "The fear that surrounds this idea is astounding. Fairweather revolutionaries?"

But other hackers have also questioned the entire pretext for the planned exposure. The original video, which said that the hackers would begin releasing the data from 5 November, claimed that it was a reprisal for the kidnapping of an unidentified Anonymous member in the coastal city of Veracruz, an oil state on the Gulf of Mexico with a major port of the same name.

Veracruz has seen a surge in drug violence in recent months in what authorities say is a battle between the Zetas drug cartel, which has controlled the territory for at least a year, and its rivals. Dozens of bodies have been discovered in recent weeks, including a 35-year-old dumped on a highway in rush-hour traffic in Boca del Rio city last month.

However, a number of doubts have been raised over the claim of the original kidnapping. There is no police report filed to link to the original claim of a kidnap: "Not one person can name the victim, the date or a witness," observed Mach2600 on Twitter.

"The tragedy that happened to the two bloggers had nothing to do with Anonymous. Sad, but [the kidnaps claims are] not them. The other kidnap victims are all accounted for in one fashion or another. None of whom were at PaperStorm."

PaperStorm was an Anonymous-organised event in December and March that encouraged members to post paper flyers in their cities. The original video claimed the Anonymous member was taken "when he was doing PaperStorm". But no confirming evidence has appeared.

With both their motivation and their motive looking shaky, some have also been questioning what Anonymous would have to aim at. "The problem is, hack what? There are no drug cartel websites, that I know of, that would be hackable," said Raul Trejo, an expert on media and violence at the National Autonomous University of Mexico.

Anonymous-style videos from Veracruz have been posted online for at least two months, but none before has drawn as much attention, and none of the others threatened violence, or promised to take on a drug cartel.

"What the video is announcing is not hacking, but rather much more violent acts," Trejo said.

As the Zetas's actions show, any fears would be well-founded. "Are we afraid? Clearly so. Do we fear for our lives? Obviously. Notwithstanding that, we think it is time to say 'enough,'" according to a statement from the purported organisers posted on the website Anonymous IberoAmerica. "We will go ahead with the operation, because people have asked us to."

The movement, if it is one, may have more success than did the bloggers in Nuevo Laredo, who posted information on drug cartel shootouts and safe houses under online aliases. Somehow, and nobody has yet said how, the Zetas apparently found out their real identities.

The Anonymous IberoAmerica website says it will form a "special task force" by invitation only to find out and publish information about cartel collaborators, a potentially deadly undertaking since rivals often kill identified members of the Zetas.

The website even included a series of security steps, such as urging members to send messages through a proxy server, and never to identify themselves as part of Anonymous.

The page also offers a supposedly secure widget to help protect users.

So far only one act has been attributed to the group: It apparently created a website decorated with jack o' lanterns that accuses a former state prosecutor of being a Zeta.

Perhaps the most telling detail is that the Anonymous IberoAmerica site is now soliciting anonymous tips on cartel collaborators. That suggests that, if the promised revelations materialise, they could be nothing more than common rumours or gossip sent in by tipsters or foes of those named.

Note: updated quote from @GeneralSec to change from "They said.." to "He said..."