More than 20,000 people have disappeared in Mexico over the past six years of a brutal crackdown on drugs during the government of former president Felipe Calderon, a civic group said.

Propuesta Civica (Civic Proposal) released a database on its website Thursday listing 20,851 people who went missing from August 2, 2006 to February 29, 2012. It said the figures were based on official data.

Among the missing were 11,201 men and 8,340 women, and about 500 others for whose gender is unknown.

Young people between the ages of 10 and 17 account for about a third of those who disappeared. About one-quarter of the victims was between the ages of 18 and 30.

The report also found a spike in the number of those who went missing last year — 7,813, up from 6,766 the year before.

Propuesta Civica said it obtained the figures thanks to a leak from a Los Angeles Times reporter.

The group warned that it could not distinguish between victims of possible violence at the hands of the government and those who perished in Mexico’s brutal drug war, which it called a “humanitarian tragedy.”

The data amounts to “one of the few sources of information to which civil society has access to begin to understand the true extent of violence in Mexico during the past six years,” Propuesta Civica said.

The database will help “build a historical memory of a process that is far from coming to an end: the violence in Mexico from the war against drugs,” the organization added.

During the Calderon government that lasted from December 2006 to December 1, the death toll from clashes between drug traffickers and between them and security forces was announced by the government on an irregular basis.

More than 60,000 people died in the war on drugs during the Calderon administration, even though he deployed the country’s armed forces to battle drug gangs.

The report showed that Mexico City and the western state of Jalisco recorded the most disappearances.

The group noted some inconsistencies that require official confirmation. For example, certain regions that have seen growing violence in recent years were shown to have a relatively low number of disappearances, including Nuevo Leon and Sonora.