CHILPANCINGO, Mexico (AP) — Thousands of teachers, activists and residents gathered in Guerrero state capital on Wednesday to protest the disappearance of 43 teachers’ college students and demand that authorities find them.

Many marched behind a banner asking “Who governs Guerrero?” a reference to the fact that local police working with organized crime have been implicated in the disappearances.

“Whose hands are we in?” said Rosa Ruth Rodriguez Mendiola, 44, a housewife from the city of Atoyac.

Investigators still had no word on whether the 28 bodies found in a mass grave last weekend included some of the missing students.

On the day the students disappeared in the town of Iguala, the mayor’s wife was finishing a speech to local dignitaries on family social services and townspeople waited for a celebratory dance afterward.

Suddenly shots rang out a dozen blocks away and people fled in a panic. Some think the incidents were related, though federal officials said late Tuesday they still have no explanation for violence Sept. 26 that killed six, wounded at least 25 and left so many missing.

Tough-looking civilians had been guarding the mayor’s wife, Maria de los Angeles Pineda Villa, a woman with alleged family ties to organized crime. A police force that state and federal officials accuse of being infiltrated by drug gangs patrolled the streets.

Into this combustible mix came the students from a radical rural teacher’s college that had defied drug cartel extortion in the past. Well-known for blocking highways and other protests, they arrived with plans to solicit donations from passers-by.

They were ending their fund-raising and meeting up to return home about the same time Pineda was finishing her speech. State officials say local police went on the attack, shooting at the buses students had hijacked for their return, as well as innocent bystanders in other vehicles.

Javier Monroy, an activist in Chilpancingo for the families of the disappeared, said the brutality of the attack “made no sense,” but could have been caused by the local cartel, Guerreros Unidos, who thought the students were going to disrupt Pineda’s speech.

Attorney General Jesus Murillo Karam declined late Tuesday to speculate on any link between the speech and the violence. 

“I am not going to single out any hypothesis until I have it confirmed which is the correct one,” he said. 

Iguala Mayor Jose Luis Abarca is a fugitive and state officials have arrested 22 city officers. His wife’s whereabouts are unknown.  In a Sept. 29 interview with Milenio Television, he said he received reports from police that the students had been attacking and robbing people who had come to the speech and dance. 

“Don’t be provoked,” Abarca said he told them. “I don’t want any kind of violence … Leave them alone, they’re just passing through.”

He said he later received reports of confrontations in different parts of the city throughout the night.

The possible massacre has focused attention on the extent to which local police forces such as Iguala’s are permeated by organized crime.

The mayor’s wife is from a family with known ties to the Beltran Leyva cartel. Prosecutors had identified her late brother, Alberto Pineda, as a main lieutenant in the cartel. He and another brother, Marco Pineda, both were on former President Felipe Calderon’s most-wanted list and were killed by rivals in 2009.

Another brother, Salomon Pineda, was released from prison last year and is believed to be the Iguala chief for Guerreros Unidos, an offshoot of the Beltran Leyva group, according to local media.

Murillo Karam said there was no hard evidence until now of the couple’s involvement in criminal activity.

“We don’t investigate on the basis of kinship but rather facts,” he said.

The chief prosecutor for Guerrero state, Inaky Blanco, said suspects have testified that as many as 30 members of the local police force were members of the Guerreros Unidos drug gang.

Blanco said the imprisoned municipal police deny killing anyone, but had bloodstains in the back of their pickup trucks. One policeman admitted handing over at least 10 detained students to “people he didn’t know,” Blanco added.

Security camera footage showed non-uniformed men forcing people into the back of a pickup truck, as others ran to escape.

One of them, Julio Cesar Mondragon, ignored his colleague’s entreaties to take refuge in the home of a local resident and kept running, said Vidufo Rosales, a lawyer for the families of the missing students.

He was later found dead on the side of the road, the skin stripped from his skull.