"We have insisted on the need for verifying and carrying out these arrest orders," Angela Buitrago, one of two current members of the Interdisciplinary Group of Independent Experts (GIEI), said in a news conference.

Some of the people who have still not been detained are public officials, she added. She did not detail how many arrests are still pending. A GIEI report accompanying the news conference said some of the orders date back more than six months.

The Attorney General's office did not respond to a request for comment.

Prosecutors last year called for the arrests of 83 military, police and government officials, among others, but 21 of the arrest orders were later withdrawn, which the GIEI at the time contested, calling the action "incomprehensible."

It also accused the government of interfering with the probe and blocking the investigation.

Buitrago added that GIEI has now sent evidence to prosecutors supporting the arrest orders that were dropped.

"It is evident within the large body of documents that there is a possibility of reactivating many of them," Buitrago said.

President Andres Manuel Lopez Obrador took office in 2018 vowing to uncover the truth around the suspected abduction and massacre of the 43 students from the Ayotzinapa Rural Teachers' College, after his predecessor's inquiry was riddled with errors and abuses.

Last year, a truth commission created by Lopez Obrador called the disappearances a "state crime" and ex-Attorney General Jesus Murillo was accused of torture, forced disappearance and obstruction of justice - the first high-level official to be charged.

The case is still ongoing and Murillo's lawyers have denied the allegations.