Police recovered 18 bodies Wednesday in a mass grave identified in a narco-video as the burial site for 20 men who were kidnapped a month ago in the Pacific coast city of Acapulco.

Fernando Monreal, investigative police chief for Guerrero state, had reported earlier that 19 bodies were removed, but he said Wednesday night that investigators miscounted the badly decomposed bodies.

Police did not yet know if the bodies found in the grave in Tres Palos, a town just south of Acapulco, were those of the men abducted Sept. 30 while visiting the resort city from neighboring Michoacan state, Monreal said.

Police began digging at the site after a video appeared on Youtube in which two men _ their hands apparently tied behind their backs and answering questions from an unseen interrogator _ say they killed "the Michoacanos" and buried them in the area.

Two bodies wearing the same clothes as the pair seen in the video were found on top of the grave, along with a sign reading: "The people they killed are buried here."

Police had not confirmed the identities of the bodies dumped on top of the grave.

In the video, the two men say they killed the "Michoacanos" in an act of revenge against La Familia, a drug cartel based in Michoacan.

The families of the 20 missing men have publicly said they were mechanics in the state capital of Morelia who saved up money to take a vacation together.

Guerrero state investigators say they corroborated the men worked as mechanics and had no criminal records. Investigators also say they could find no evidence linking the men to any gang and have speculated the group may have been targeted by mistake.

The kidnapping was one of the biggest blows yet to Acapulco, which has seen an increase in drug-gang shootouts, beheadings and kidnappings. Even Acapulco Mayor Jose Luis Avila Sanchez recently urged residents to stay indoors after nightfall, an extraordinary pronouncement in a city that depends on nightclubs, bars and restaurants.

If the video's claim is confirmed, it would be a chilling example of a growing trend that has added a new dimension of terror to Mexico's bloody drug war: cartels releasing footage of kidnapped people admitting at gunpoint to crimes from extortion to murder. It is often impossible to determine the veracity of confessions given under duress.

In the boldest case, a video emerged less than two weeks ago showing the kidnapped brother of Patricia Gonzalez, the former attorney general of northern Chihuahua state. In the video, the brother, Mario Gonzalez, says his sister protected a street gang tied to the Juarez cartel and was behind several murders.

Gonzalez, who had been kidnapped days earlier, made the statement while sitting handcuffed in a chair surrounded by five masked men pointing guns at him. His whereabouts remain unknown.

Patricia Gonzalez denied any links to drug traffickers and said she is sure her brother spoke out of fear.

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Associated Press writer Mark Stevenson in Mexico City contributed to this report.